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-A-^ C- 

















Si c 







The Cbrbbko-Spinal Axis 
The Spinal Cord .... 
External form - . 


Internal structure .... 
Grey Matter .... 
Central Canal .... 
White Matter .... 
Features of different regions . 
Microscopic structure 
General structure .... 
Distribution of Ner\'e- Cells 
of Anterior Horn . 
of Clarke's Column 
of ^liddle Cell-Column . 
of Posterior Horn ; Solitary Cells 
Commissures ..... 
Central Canal .... 
Origin of Spinal Nerves 
Anterior Roots .... 
Posterior Roots .... 
Collateral Fibres 
Conducting Tracts .... 
Methods of investigation 
Antero-lateral Column . 
Posterior Column 
Degenerations in Spinal Cord . 
From section of Posterior Roots . 
From Lesions of the Brain 
From Lesions of the Cerebellum . 
From Lesions of the Cord 
The Brain or Fxcephalon . 
The Medulla Oblongata and Pons 


The Medulla Oblong.a.ta 
External characters .... 
Posterior Area .... 

Lateral Area 

Olivary Body .... 

Anterior Area 


The Pons Varolii .... 

Fourth Ventricle .... 

Internal structure of Medulla Oblongata 

Closed part .... 

Ventricular part .... 

Nucleus of Olivary Body . 

Formatio Reticularis 

Arched Fibres .... 

Internal structure of Pons Varolii 

Course of Fibres from Cord through Bulb 

and Pons .... 
Transition from Pons to Mid-Brain . 



























The Cerebellum 69 

External form 69 

Upper surface 71 

Under surface 74 

Arbor Vit«B 83 

Commissural Fibres in White Matter 84 

Peduncles 84 

Microscopic structure , . . . 
Degenerations following Lesions of. 
The Mid-Brain and Inter-Brain . . 
Aqueduct of Sylvius .... 

Third Ventricle 

Central Grey Matter of Aqueduct . 
Crura Cerebri 


Substantia Nigra 


Tract of Fillet . . . 
Dorsal part of Mid-Brain 

Corpora Quadrigemina . . . . 

Posterior Commissure .... 

Geniculate Bodies 

Optic Thalami 

Trigonum Habenulse 

Subthalamic Tegmental Region . 

Pineal Body 

Posterior Perforated Space . 

Corpora Albicantia 

Infundibulum, and Tuber Cinerenm . 

Pituitary Body 

Lamina Ciuerea . . - . . 

Optic Tracts and Chiasma . . . 

The Lateral Ventricles : Corpora 

Striata : Cerebral Hekcispheres 

Lateral Ventricles 

Corpus Callosum ... 

Septum Lucidum 


Tjenia Semicircularis .... 

Corpora Striata 

External Capsule 


Internal Capsule 

Cerebral Hemispheres . . 

External form 


Frontal Lobe 

Parietal Lobe 

Occipital Lobe 

Temporal Lobe 

Central Lobe or Island of Reil . 

Limbic Lobe 

Olfactory Lobe 






















The Cerebral Hemispheres— coTi/mt^. 
Variations in Fissures and Convolu- 
tions i6i 

Causation of Gyri and Sulci . . . 162 
Structure of White Matter . . 163 

Structure of Grey Matter , . . 166 
Differences of structure in different 

parts 172 

Measttrbments of the Brain . . . 176 

Dimensions 176 

Extent of Grey Cortex . . 176 
Thickness of Cortex -177 
Weight 178 


Membranes of Brain and Spinal Cord 181 

Dura Mater 181 

Subdural space 184 

Pia Mater 184 

Arachnoid Membrane . . 187 

Subarachnoid Space . . .187 

Ligamentum Denticulatum . . . 189 
Glandulse Pacchionii . . .190 

Blood-vessels of Brain and Spinal 

Cord 191 

Spinal Cord 191 


Lymph-Paths of Brain and Spinal Cord 




The cerebrospinal axis is divided into tlie 
brain or encephalon, the enlarged part within the 
Bknl), and the spinal cord within the Tertebral 
canal. It is symmetrical in form, coneieting of 
a right and a left half, separated to some extent 
by fisenrefl and cavities, but united hj Tarioas 
pottions of white and grey nerrouB sabstance 
which cross from one side to the other, and 

Kg. 1.— ?IIW or IHI aiHIBHO-SFIKAL ixis. (After 

Bourgeij,) I 

Tbe right halt of the erauiaai and trunk of the bod; 
hu bMD remoTcd b; a reitical Kctioii ; the membranes af 
tbe right side of tbe bniD and apinal tord have b«en elearsd 
awaf, and the iDOts and first part of tbe fifth and twelfth 
cmniid Derrea, tind of all the apinal nerves of tbe right 
side, hne beea dissected out and laid scparatel;i on the 
wall of tbe aknll and on tbe aeTeral vertebm oppaeite to 
th« place of their natural exit from the cranio-Bpinal esvity. 

P, T, 0, frontal, temporal and occtpiul lobes of eere- 
bmm ; C, cerebellum ; P, poos Varolii ; m o, mednUa 
oblongata ; m i, m t, paint to tbe upper and lower 
eitremitiea of tlie spinal marrow ; c t, oo tbe last lumbar 
vertebral spine, marks tbe canda equioa ; T, the three 
principal branches of the nerrua trigemiuns ; C i, the 
sub-occipital or first cenical nerve ; C viii, the eighth or 
lowest cervical nerve ; D T, the first dorsal nerve ; D jeji, 
the last dorsal ; L i, the first lambar nerve ; L v, the laat 
lambar ; S i, the first sacral nerve ; 8 v, the fifth ; Co i, 
tbe coccygeal nerve ; f, tbe left sacral plexus, 

form the e<mnmmres of the brain and spinal 

The ccrebro -spinal axis is enveloped within 
the skull and vertebra! canal by three counective 
tisane membranes, between which are spaces 
occupied by a clear fluid (cerebro-spinal fluid). 
These envelopes, which will be described later, 
are, Ist, a firm fibrous membrane named the 
dura tnaler, which is placed most estemally ; 
2nd, a delicate membrane called the arachnoid; 
and, 3rd, a highly vascular membrane named the 
pia mater, which is next to, and closely invests 
the eur&ce of the brain and cord. 



The spmal cord or xpinal marrow (medulla spinalis) is about 18 inches (45 

eentimeters) long, and extends fropi the margin of the foranien magnnm of the occi- 
pital bone to about the lower part of the body of the first lumbar vertebra. Above, 
it is continued into the bulb (medulla oblongata) ; below, it tapers conically and 
ends in a slender filament, the filum lerminale or central ligament of the spinal cord. 
Although the coi-d usually ends near the lower border of the body of tbe first 
Inmbar vertebra, its termination is sometimes a little above or below that point, as 

AUD or th:s to tbi tertebsal oanai. (Kej and BcUiiu.) 
A, throngh tbe fifUi cemcal vertebra; B, through the tenth dorsal vertebra : C, through the Ant 
lambar vertebia nad the foramen of exit of the twelfth dorsal aerve-roota ; D, tbroujjb tbe diak Iwtveen 
the MCODcI and third lumbar vertebra ; B, through the &nt sacral vertahra. In A, B, and C, tbe cord, 
covered b; pia mater, is eeeu in the centre, with the ligamentum denticulatum attached to it oa either 
Hide : the nerre-rootB on either side form small groups which, since they past obliqiiel; downwards to 
their foramina of exit, are cut across ; the dura matral sheath ii separated bj a considerable space from 
the cord, and by a quantity of loose areolar and fatty tissue from the wall of the vertabral canal. This 
tissue is in smaller amount In C. D and E are below the termination of the cord, and show sections of 
the nerve-bundles of the canda equina within the dural sheath, which is lery large in D, but compara- 
tively small in B, the vertebral canal in the latter being largely occupied by adipose tissue. Id this are 
seen the seditions of two large veins. The arachnoid is not represented in any at these sectiaas- 

opposite to the last dorsal or to the second lumbar vertebra. The position of the 
lower end of the cord also varies according to the state -of curvature of the vertebral 
column, in the flexion forwards of which the end of the cord is slightly raised. In 
the fcetus, at an early period, tbe embryonic cord occupies the whole length of the 
vertebral canal ; but, afler the third month, the canal and the roots of the lumbar 
and sacral nerves begin to grow more rapidly than the cord iteelf, so that at birth the 
lower end reaches only to the third lumbar vertebra. After birth the thoracic part 
of the cord lengthens proportionately more than the other parts, so that in the infant 
the roots of the lower dorsal ncrces come off relatively higher up than at a later ^ 


The cord is enclosed in the vertebral canal within a sheath {fheca) considerably 
longer and larger than itself, formed by the dura mater, and separated from the walls 
of the canal by venous plexuses, and much loose areolar tissue (tig. 2). The cavity of 
the sheath between the pia mater and the dura mater is occupied by cerebro-spinal 
fluid, and is divided by the curtain-like arachnoid into the spaces, subdural and sub- 
arachnoid, above mentioned. Within the latter the cord, covered closely by pia 
mater, is suspended, being kept in position by a ligament on each side (ligamentnm 
denticulatum), which fixes it at frequent intervals to its sheath, and by the roots of 
the spinal nerves which pass across the space from the surface of the cord towards 
the intervertebral foramina. 

The spinal nerves come off in pairs at intervals along the cord. The portion 
of spinal cord to which each pair of roots is attached is termed a " segment," but 
there is in man and mammals complete continuity from segment to segment, and 
not even a sign of constriction between them. Each nerve is attached to the surface 
of the cord by two roots, one of which is anterior or ventral and non-gangliated,^ the 
other is posterior or dorsal and is provided with a ganglion. The uppermost two 
or three nerve-roots cross the subarachnoid and subdural spaces nearly horizontally 
(figs. 1 and 5), but the rest pass across with a more and more oblique downward 
inclination until their direction is almost vertical, and indeed the lower part of the 
theca below the termination of the cord (fig. 2, n, e), is occupied by the descending 
roots of the lumbar and sacral nerves, passing to the foramina between the corre- 
sponding vertebrae. This mass of nerve-roots, which conceals the delicate filum 
terminale, is named the cauda equina (figs. 4, 5, 6). 

The relation between the spines of the vertebras and the places of attachment of 
the nerve-roots to the cord is illustrated by the appended diagram (fig. 3) from 
Reid, which is founded upon observations made on six adult subjects. From this it 
will be seen that there is a much larger amount of variation than might have been 
supposed. This is especially the case with the dorsal nerve-roots, some of which 
show variations of their position of origin extending over a distance covered by as 
many as three spinous processes. Certain general facts can, however, be made out 
which are not without practical interest. Amongst these are the position of the 
second cervical nerve — opposite the arch of the atlas ; that of the first dorsal or 
thoracic nerve, opposite the sixth or seventh cervical spine ; that of the seventh 
thoracic nerve, opposite the fourth or fifth dorsal spines, and of the sacral nerves, the 
range of which extends from the eleventh dorsal to the first lumbar spine. The 
line of origin of the sacral nerves very nearly corresponds in vertical extent with the 
body of the first lumbar vertebra. 

No doubt this variation is largely accounted for by the variations in length and 

obliquity of the spinous processes of the vertebrae, and accordingly we find that 

there is least fluctuation of relative position at the top and bottom of the series. 

The anterior and posterior (ventral and dorsal) nerve-roots belonging to the same 

. segment of the cord leave it practically at the same level (Reid). 

The cervical enlargement (see next page) about corresponds in vertical extent 
with the spines of the cervical vertebrae, while the lumbar enlargement corresponds 
with the spines of the tenth, eleventh, and twelfth thoracic and the interval between 
the last named and the first lumbar. 

In section the cord is nearly circular, especially in the thoracic region, but it is 
somewhat flattened before and behind. In the thoracic region, it measures about 
ten millimeters (0*4 inch) from side to side, and about eight fi-om before back. The 

^ Some animals (e.^. , cat) have a few ganglion-cells interpolated amongst the fibres of the anterior or 
yentral nerve-roots. Hoche finds that in the anterior roots of the lower lumbar and sacral nerves of 
man, just at their junction with the cord, ganglion-cells, like those of the posterior root, are almost 
constantly present, lying singly or in groups, and connected with some of the issuing norve-fibres by a 
T-shaped junction. 

B 2 


Fig. 3. — DlAQKlM 

(After R. W. Beid.) 

IRS. (Alleo Thomsoa.) i 

If] of the roots of the aerv«. The Itlifann piolosiui- 

I. C, a traBsveree aectioa thraugh the middle of the 


mednlla oblongkta ; D, > teliaa throogk tLe middle of ike 
ceirical enJaigcinent of the coni ; E, throngh the appai 
donal region ; P, throagb the lower darnU TexioD ; 0, throogb 
tb« middle of the lumbi^enlargameiit; uidH, near the lower 
end of the conug mednlliiris. 

1 to 6 refer to paita of the medalLi abloDgftta ; the 
remaining nnmbeis to parts of the Bpinal cotd. 

I^ pjiAmida ; J\ their decunation ; 2, olivarj Inylieii ; 
S, lateral columne; i, fourth ventricle; 4', calunaB BCrip- 
torias ; 5, fnoicnloB gracilis ; S, fnnicnlni caneatoB ; 7, 
7, interior median finaaro of the ipinal cord ; 8, S, poitero- 
lateial groove oorrespoading to ihe att«chmentfl of the poa- 
terior nerve-roots ; 9, 9, poaterior median fisenre ; x , taper- 
ing extremity of the cord ; x , x , in B', Slum tenninale. 

cord is not, however, ot uniform diameter 
thronghont, but ia swollen out in the cervical 
and lower dorsal regione, two enlu^ments 
being thereby produced — an upper or cervical 
(brachial), and a lower or lumbar (crural) (fig. 4). 
Of theae the cervical enlargement ie of greater 
size and extent than the lumbar. It extends from 
the upper limit of the cord to the bod; of the first 
or second thoracic vertebra ; it is largest oppo- 
site the fifl^h or sixth cervical vertebra, where it 
measures from 13 to 14 mm. from side to aide. 
The lower or lumbar enlai^ment begins at the 
tenth thoracic vertebra, is lai^est opposite the 
twelfth (11 — 13 mm. across), and from this 
point becomes gradually smaller ; ite antero-pos- 
terior diameter is more nearly equal to the 

THSna (Allen Thomaon.) }. 

The spinal nervea are enumerated in order on the right 
aide ot Om figure. Br, brachial plema ; Or, anterior 
CTor*], 0, obtorator, and Sc, great sciatio nerrea, coming 
off from Inmbo-iacral plexus ; x, x, Blam tenninale. 

a, b, e, BDperior, middle and inferior cervical ganglia of 
the ajmpKtbetic, the last united with the Gnt thoracio. 
d ; d', the eleventh thoracic ganglion ; I, the twelfth 
thoracic (or Aret lumbar); below 1 1, the chain of lacral 

tranaveise than is tbe case in the cervical en- 
largement. Below the lumbar enlargement the 
cord tapere in the form of a cone (amm medul- 
larie), from the apex of which the small fili- 
form prolongation la continued downwards. 

The cervical and lumbar enlargements have 
an evident relation to the large size of the 
nerves which supply the upper and lower limbs, 
and which are connected with those regions of 

the cord. At the commencement of its develop- . ^g 

ment in the embryo the spinal cord is destitute 

of these enlargements, which, in their first appearance and subsequent progress, 
correspond with the growth of tbe limbs. 

The tenmnal filuaaat (filum terminale, central ligament) (fig. C, h, b) descends 


in the middle line amoaget the nerves composing the cauda equina, and, reaching 
the lowei end of the sheath opposite to the second sacral vertebra, perforates the dnra 
mater, and receiving on investment from it, passes on to be attached with this to the 
periostenm of the lower end of the sacral canal, or to the back of the coccyx. It is 
a prolongation of the pia mater, enclosing for tibout half its length an enlarged 
continnation of the central canal of the cord (see p. 9), with a little grey matter 
near the upper end. Below the termination of the canal, the fiium is mainly com- 
posed of connective tissue, with hlood-vessels prolonged 
from the anterior spinal vessels, and on either side there 
run in it three or four small bundles of meduUated nerve- 
fibres, some of which have a few ganglion-cells. These 
nerve-buadles are regarded by Rauber as representing 
rudimentary coccygeal nerve-roots. They have no con- 
nection with the coccygeal nerves proper. 

The filum terminale is distinguished by its silvery 
hue from the ner\*es among which it lies. 


ThonuoD. ) i 

The sheath tuts been opened from behind and stretched towardB 
the Bides ; on the left side all the roots of the nerves are entire ; on 
the right side Lothroota of the firat and second liimliar nenes ore entire, 
while the rest have been divided close to the place of their pssaage 
through the sheath. Ths hones of the coccyx ate sketched in their 
natnial relative position to show the place of the filum terminale 
aud the lowest nerves. 

a, placed on the posterior median fissure at (he middle of the 
lumbar enlargement of the cord ; b, b, the terminal filament, drawn 
sUghtl; aside h; a hock at its middle, and descending within the 
duntl sbeatb ; Ir', b', its prolongation beyond the sbcalli and upon 
tbo back of the coccygeal bones ; e, the dural sheath ; d. double 
foramina in this for the separate passage of the ventral and doreal 
(anterior and posterior] roota of each of the nerves ; «, ligamentum 
denticulatum ; Dx, and DxiT, the tenth and twelfth thoracic (dorsal) 
nerves ; Li, and Lv, the first and fifth lumbar nerves ; Si, and 8v, 
the first and fifth sacral nerves ; Ci, the coccygeal nerve. 

Flsanres. — The spinal cord is incompletely divided 
into a right and left half by two fissures which pass in 
from the middle of the anterior and posterior surfaces, 
and penetrate through the greater part of its thickness. 
Of these two median fisgures the anterior or ventral (fig. 
7, 1) is wider and therefore more distinct than the pos- 
terior or dorsal, although it does not, in most parts, 
penetrate to more than one-third the thickness of the 
cord, while the posterior fissure may reach more than 
half-way from back to front. The anterior contains a 
fold of the pia mater and also many blood-vessels, which 
are thna conducted to the centre of the cord. At the 
bottom of this fissnre is a transverse connecting portion 
of white substance named the anterior or white com- 

* The posterior (fig. 7, 2) is not an actual fissure, for, 

although the lateral halves of the cord are quite separate 

dorsally, there is not so much a fold of the pia mater between them, as merely a 

septnm of connective tissue and blood-vessels prolonged from that membrane whioh 


passes in nearly to the centre of the cord {posterior septum). Ite position is marked; 
especially in the lumbar enlai^ement and in the cervical region, bj a saperfioial 
f BiTow. At its eiid is the posterior or cfret/ eommitsure. 

Besides these two median fissures, a lateral furrow is seen on each side of the cord, 
corresponding with the line of attachment of the posterior roots of the spinal nerves. 
It is named the poatero-lakral groove (fig. 7, c, 4). Each lateral half of the cord is 

Kg. l.-hurnxKin vuwa of a puriiok 

(Allen Thomson.) 

In A, the anterior or ventml aurfaoe 
of the specimen a thonti, the anterior 
nerre-rootof the right Bide haring been 
divided ; in B, a riew of the right side is 
given ; in C, the npper surfiioe is shown ; 
in D, the neive-roota and ganglion are 
■hewn from b«low. 1. the anterior 
median Siunre ; S. poeterior median 
fissnie ; S. antero-t&teral impression, 
OTCT wbioh the bundles of the anteriui- 
nerve-root are seen to spread (this im- 
pression is too distinct in the figure) : 4, 
posCero- lateral groove int« vhich tl>e 
bandies of the posterior root are seen tti 
sink ; 6, anterior root ; 5', in A, the 
anterior root divided and turned up- 
trards ; S, the posterior root, the fihrev 
of which pass into the ganglion, 6'; 7. 
the united or compound nerve ; T, the 
posterior primary bmnch, seen in A and 
I) to be derived in part from the ante- 
rior and in part from the posterior root. 

divided saperficially by the postero-lateral groove into a posterior and an antero- 
lateral part. The attachmeDt of the anterior roots, however, subdivides the latter 
into anterior and lateral portions. 

An anterD-lateral groove has sometimes been described in the line of oriiciii of the anterior 
roots of the nerves, but nsnaUy has no real existence. The flbres of these roots in fact, 
unlike the posterior, do not dip into the spinal cotd in one narrow line, but spread over a 
space of some breadth. 

On the posterior surface of the cord, at least in the upper part, there is on eacli 
side of the middle line a slightly marked longitudioal furrow (fig. 11) situated about 
one millimeter from the posterior median fissure, and marking off, in the cervical 
region, a slender tract, the postero-mesial column. This sulcus, which ia better 
marked in some individuals than in others, is termed the posterior mtemtediafe 
farrow. An incomplete connective tissue septum {posterior intermedial septum) 
extends from the liurow into the white sabstance of the cord. The Urger remaining 
part of the posterior column is termed the postero-lateral column. 

Qrtcf mattar, — When the spiaal cord is cut across (figs. 8, 11,14) it is seen that 
the grey matter occupies the more central parts, being almost completely enclosed by 
the white matter. The grey matter appears in the form of two irregularly crescentic 
portions on either side, united across the middle line by the posterior grey commis- 
eore before mentioned, so that its section may be compared in shape to the letter H. 


The concave side of each lateral crescent faces oatward, and in oonseqnence of the 
depth of the posterior median fiaanre the commiasnre of grey matter joins the creecenta 
nearer their anterior than their posterior ends, except in the lambar region of the cord. 
The tvo horns or comua of each crescent are named from their position anterior 
and posterior (or, better, ventral and dorsal) ; the anterior or ventral horn (fig, 8, 
a. c) is the shorter and broader, and is everywhere separated from the surface of the 
cord by white matter which is traversed by the bundles of the anterior roots at the 
part where these enter the cord. The posterior or dorsal horn (p. c) is longer and 
narrower, and tapers almost to a point (apex comu posterioris), which closely 

a, anterior median Graure ; p, poHtArior'inedian fisflure ; p, v, 
ponlerior Derve-rooU entering iX tbe postera-Iateral grooTe; a, e, 
luiterior comn of gre; mutter ; p, c, poBteriar conia : >. inler- 
medio-Utenil bract (lateral cornu) ; p, r, procesaaa r«ttCnlKrU ; e, 
posterior vesicular calnmn of Clarke ; I, pia-outral •eptum form- 
ing tbe lateral boundarj of the postero-mesiat columa. 

approaches the external snrrace of the cord at the 
pOBtero-lateral groove, with which it is connected 
by a process of the superficial nenr(%lia which here dips in towards the horn, 
but is interrupted by a stratum of fine nerve-fibres known as the marginal 
bttmUe. The posterior liom is slightly narrowed at its base {cervix comu) ; from 
that place it gradually expands into the main part of the horn {caput comu), and 
from this it tapers in the way just noticed. Near its tip the caput comu has a 
peculiar semi-transparent aspect, an appearance due to the substantia gelatinosa of 
Rolando (fig. 14), which forms a kind of cap to the cornu. The part of the grey 
crescent between the two horns is known as the intermediate grey sul>stance (Gowers). 

Near the middle of the outer surface of each crescent the grey matter is less 
sharply marked off than elsewhere from the white matter ; portions of grey matter 
extending into the lateral white column and uniting with one another into what in 
sections appear like a network enclosing portions of white substance {p. r.). This is 
known as the processus retirularis ; it is best marked in the cervical r^on (fig. 14). 
At the postero- lateral part of the anterior horn, immediately in front of the 
proceaaua reticularis, the grey matter forms in tbe upper dorsal (thoracic) region 
(fig. 11, J> 1) a somewhat pointed triangular projection, which is sometimes distin- 
guished as the lateral horn but is better known as the in fermedio- lateral tract of 
liockhart Clarke {intermediate process of Gowers) (fig. 8, i). Above, in the cervical 
region, this blends with and forms part of the enlarged anterior horn. This is 
also the case iu the lumbar enlargement, but in the sacral r^ion the lateral horn 
again becomes distinct. 

The grey crescents vary in form in different parts of the cord (see fig. 9). In 
the dorsal (thoracic) region both anterior and posterior cornua are narrow. In the 
cervical and lumbar regions the anterior cornua are large and broad. The posterior 
cornua are narrow in tbe cervical and thoracic, but very broad in the lumbar region. 
The grey matter is seen in a scries of sections to be most abundant in the lumbar 
region of the cord, and least in the thoracic. 

It is clear that what appear in section as irregular crcsceutic areas of grey matter 
are in reality long irregularly fluted columns, and that the commissural buid uniting 
the convex edge of tbe crescents is a flattened expansion, connecting the columns 
along their whole length. But it is both customary and convenient to speak of the 
various parts of the grey matter of the cord according to their appearance in sections, 
although the term " columns " is very generally applied to what appear in section 


tm groups of nerve-cells, occnrring in diflerent parts of the gnj matter, as well as 
to the several portions of the white matter imm^iatel; to be described. 

Csntnd oulkL — Extending throngh the whole length of the spinal cord, in the 
substance of the grey commisatire, there is a miante canal (fig. 8) which, in sections 
of the cord, is barely visible as a speck, with the naked eye. It is continued above 
into the medulla oblongata, where it gradually approaches the posterior surface and 
eventually opens out at the calamns scriptoriiis of the fourth 
ventricle. At the lower end of the cord, near the extremity 
of the conus medullaris, it becomes enlarged, and shaped like 
the letter "f, and is stated by some observers to open on the 
dorsal or posterior surface of the cord ; but this is denied by '"^ 9.— Skctiom or 
others. This central canal, though minute, is an object of MUiK tbb ixtbk- 
considerable interest as a typical part of the Btructure of the ""f o» tbb canus 
cord, since it is the permanent remains of the epiblastic canal "fi^'iJbont'ai/dw^ 
from which the spinal cord is developed. It is more distinct meten. 
in lower vertebrata than in mammals. 

Whit* nifttUr.— The white substance of each half of the cord completely 
encloses the grey matter except opposite the posterior horn. This last therefore 
serves to separate otf a smaller pogtrrior u-hile column, which is somewhat wedge- 
shaped in section and is bounded internally by the posterior median fisenre, from the 


BioriaBAL iXEis or tat ssvrbii, ntTEKine kebve-buotb (adapted fram Ludvig and Waroschiloff). 
(B. A. S.) 

The sectional arem ot the sevcraJ entering narve-roots {n.r)  well as tho eitont of the grej mutter 
(^), and of the lateral, posterior, and anterior colgmns of while matter {L e., p. c, and a. c), are 
repraKnted in euperposed eurres, the common abaeiasa of vhich (abt.) a interwcled nt equal interrale 
by ai man; ordinate! aa there are pairs of ipinal nerres. In the orilinatea each uiillimeter above the 
abacian npresentu about ods square millimeter of secUonal area. 

rest of the white substance which forms a large aniero-laferal while column (figs. 7 
to 9). The antero-lateral column is sometimes arbitrarily divided into anterior and 
lateral white columns, the place of passage of the bundles of the anterior nerve-roots 
being taken as the limit between the two ; but since these are scattered over a 
considerable part of the transverse section it is clear that the limit cannot be 
distinctly fixed. 

The white substance ia traversed by imperfect septa of connective tissue 
prolonged inwards from the pia mater. Most of these are irregular and somewhat 
variable in position, with the exception of one in the cervical region extending 
inwards towards the grey commissure from the sulcus before described as bounding 
the poetero-mesial column. This, the posterior intermediate septum before men- 
tioned (p. 7) (fig. 8, «) cuts off a small portion of the posterior column next to the 
posterior median fissure, corresponding to the projection of the postero-mesial column 
on the surface. 


The lateral symmetry of the spinal cord is not always perfect. The white columns 
especially are found slightly to vary, the variation being generally caused by the 
fact that the amount of the pyramidal tracts of white matter diflPers somewhat on 
the two sides of the cord (see p. 24). More rarely considerable malformations 
have been found to occur. 

The white matter of the cord, especially that of the lateral and posterior columns, 
increases gradually in amount from below upwards, receiving a considerable accession 
opposite the roots of the larger nerves which supply the limbs. These relations are 
strikingly shown in the appended curves (fig. 10) which have been constnicted by 
Ludwig and Woroschiloff from measurements by Stilling. The amount of the grey 
matter in the different regions is also given, as well as the sectional areas of the 
roots of the spinal nen-es. It is seen that opposite to the origins of the large nerves 
there is a marked increase in the amount of grey matter. 

The anterior or white commissure is likewise proportional in size to the entering 

Characteristic features of the different regions of the cord. — In the 
sacro-coccygeal region the bulk of the spinal cord is formed of grey matter which 
has a comparatively thin mantle of white substance surrounding it. The posterior 
cornua are nearly as thick as the anterior, and the isthmus of grey matter is relatively 
thick. The lateral comu (in the sacral region) is well marked. Both here and in 
the lumbar region the number of nerve-cells imbedded in the grey matter is rela- 
tively very large, a fact which is probably connected with the circumstance that 
these regions are concerned with numerous and important reflex acts. 

In the lumbar region the white matter begins to predominate, owing chiefly to 
the accession of the large nerve-roots of the sacral and lumbar plexus, many of the 
fibres to and from which are now running down and up the white columns of the 
cord. The posterior horn and the grey matter in general is still thick, although in 
the upper part of the lumbar region it has become thin and has more of the 
character which is met with in the thoracic region. The lateral horn is not distinct. 
The outline of the cord is beginning to be more circular, a shape which is maintained 
as far as the second thoracic segment. 

In the dorsal or thoracic region the chief characteristic is the relatively small 
amount of grey matter, which forms two long slender crescents united by a narrow 
isthmus, which both here and in the cervical region is placed nearer the ventral than 
the dorsal aspect of the cord, whereas in the lumbar and sacral regions it Ues near 
the middle of the dorso-ventral axis. The white matter is absolutely as well as 
relatively greater in amount than in the lumbar region. The lateral horn forms a 
distinct acute prominence throughout the whole of the thoracic region, but is most 
marked in the upper part. Clarke's column (see p. 16) is also to be seen near the 
base of the posterior horn : it is most prominent at the lower part of the thoracic 
region. In the upper part the postero-mesial column begins to be marked off from 
the postero-lateral. 

The cervical region is characterized by the fact that the cord, except at the upper- 
most part, is of large size and tends to be somewhat flattened dorso-ventrally. The 
increase in size affects both grey and white matter. The postero-mesial column is 
now sharply marked off from the postero-lateral. Fibres of the spinal accessory 
roots may be seen passing out from the lateral cornu. A reticular formation is seen 
at the outer edge of the grey matter. Both the lateral and anterior cornua are large 
and are fused together to form a mass of grey matter, triangular in section, and 
tapering off dorsally into the base of the posterior horn. This horn and the substance 
of Rolando are but slenderly developed, contrasting with the large development of 
the same parts in the lumbar enlargement. The isthmus is thin, and the central 
canal flattened dorso-ventrally. 



III the uppermost segments (upper part of the cervical enlargement) the grey 
matter is again diminiehed in amount and the cord has become circular in outline, 
as in the dorsal region. The section has however the other cervical characteristice, 
and there is a much mure strongly marked anterior commissure than in the thoracic 
cord. Opposite the first cervicij nerve-roota the cord begins to merge into the 
medulla oblongata or spinal bulb, and the passage of the pyramidal fibres from the 
pyramids on one side of the bulb to the lateral tract on the other side of the cord 

Fig. 11.— TUKSTIM 

Ths letUn ind nninbtn indicate Uie pocilioi 
Sac. 4 of Itli ucisl : L3 of 3rd Inmbar, and bo od 
celli within it are indicated by dots. 

tends partially to ohhterate the anterior median fissure and to cut up the grey 

In the cervical region the nerve-roots leave the cord nearly at a right angle and 
close together ; in the other regions at an angle vrhich is more or less oblique, the roots 
being directed from the intervertebral foramina upwards towards the cord ; in the 
thoracic region they succeed one another at relatively longer intervals than 



The white sabBtaiioe of the Bpiaal cord is almost wholly composed of longitndinallj 

conraing medullated nerve-fibres, which io carmine-sfcained transverae sectiona of 
the cord (flg. 12) appear as clear liog^ with a etaiaed dot — the eection of the azis- 
cyliader — either in the middle of the ring or shifted somewhat to one aide. The 
fibres vary much in size, and in many pai-t£ of the section larger and smaller fibres 
are intermixed, but some parte are characterised by containing many lai^ fibres, 
others for the most part small fibres. The lai^;est fibres are in the ciroomfeteatial 
part of the anterior and lateral columns (and especially in the direct cerebellar tract), 
the smallest in the part of the lateral column in the neighbourhood of the proceesna 
reticularis, in the marginal bundle of Lissaner near the apex of the posterior horn, and 
in the postero-mesial column. Very small fibres also occur scattered over the white 


HlOHLT MAQNiniD. (E. A. S.) 

a, a, guperfidol nenroglia ; b, b, traiurerM aitctian of pnrt nf tha lateral column of the conl (direct 
cetebelUr tract). The diik points are tha aiin-ejlinders, ;iiiii the clear Breaa the mednllarj substuice 
of the nerre-Gbres : the superficial neuroglia exhibits the appearance of a fine networlc in vhich onlj the 
naclei of the nsuroglia-cella are seen. One or two corpora amj/lt%cta (c. a) are embedded in the nenioglia, 
vbicb eitenda inwarda among the nerve-fibres. 

substance, especially in the anterior column. The white columns are imperfectly 
divided into secondary columns by incomplete septa of fibrillar connective tissue 
which are prolonged inwards from the inner layer of the pia mater, and convey 
blood-vessels to the interior of the cord. 

Immediately beneath the pia mater and closely investing the cord externally is a 
layer of what in the fresh condition appears a bomogeneons snbstance with nuclei 
embedded in it here and there. In sections of the cord hardened in alcohol or 
chromic salts, the substance in question is finely reticnlated (fig. 12, a, a). The layer 
which it forms is very thin over some parts of the surface hut comparatively thick 
in others, and where the pia septa pass into the cord, it accompanies and invests 
them and their ramifications in the white substance, passing with them between the 
irregular bundles of nerve-fibres. Not only does this subpial reticular substance 
accompany the prolongations of the fibrillar tissue and largely assist in forming the 
incomplete septa above mentioned, but it extends independently amongst the indi- 
vidual nerve-fibres, occupying the interstices between them, and ser%'iDg as a uniting 
medium in which they are embedded. Hence it was named by Virchow the 
neuroglia (nerve-cement). The nuclei in it belong for the most part to branched 
fibrillated cells (neuroglia-cetls) which occur in considerable numbers and may be 


said to form the tisBiie ; some which are more conspicnons are known as the cells of 
Deiters ; they appear stellate in section and are fonnd in the larger interstices 
between the nerve-fibres. Along the line of origin of the posterior roots the super- 
ficial neoiogliadipe inwards towards the horn of grey matter, and expands within it to 
join the gelatinous substance of Rolando. This, as before mentioned, presents a 
transparent jelly-like appearance in the fresh condition, but in sections of the 
hardened cord it is finely reticular, containing numerous neuroglia- cells. Some of 
the bundles of nerve-fibres of the posterior root traverse this subatance, and it 
contains many nerve-cella ; these are mostly of small size, but here and there one of 
larger dimensions is met with. 

In the constitution of the rest of the comna the neuroglia takes part to a far 
less extent than in the substantia gelatinosa. It is true that it is prolonged both 
from this and from the white substance into the grey matter, and pervades the 

Fig. 13, — Section or tbi tao- 

c, cenUal oaal ; v, Tentral or 
Mitedor ; d, doraal or pralerior 
mrfaM. The apangioblnsts ftlone 
ar« eolaareil and are Been to 
extend from the central canal to 
the periphery of the conl. Some 
appear to be detached and in pro- 
OGBB of eonvenioo into nenroglia- 

latter throughout in every 
part. But it is in great 
measure obscured by the 
proper nervous elements, 
which in the grey substance 
comprise both cells and 

fibres. In the first place are found multipolar nerve-cells, many of large size, 
scattered singly or occurring in groups throughout the grey substance. In connec- 
tion with these and especially accumulated around the cells and cell-groupe, is an 
interlacement of the finest nerve-fibrils, which is derived partly from the ramified 
processes of the nerve-cells, aud partly from the ramification of nerve-fibres or of 
collateral fibres which enter the grey matter from the nerve-fibres of the white 
colnmns. Occupying a considerable portion of the grey matter, are nerve-fibres, 
mostly of the medullated kind ; these and the axis-cylinder processes of the nerve- 
cells traverse the grey matter in different directions, coursing for the moat, part in 
bundles which intercross with one another, and confer on the grey matter a spongy 
appearance. Hence it is sometimes known as the subslantia spon^iosa. 

Some of thew bundles, which ate fairly conitaut in position in many seclionB of the spinal 
cord, have recently been described by Pal (see BibUography). 

The structure of the neuroglia is described in the part of this work which deals 
with General Anatomy (Vol. I., p. 322). It is developed from the spongioblasts of 
His (see Embryology, Vol. I., p. 57), which at an early period of development 
extend from the central canal in the middle of the grey matter to the periphery of 
the cord {fig. 13). (The same holds good for other regions of the cerebro-spinal axis). 
At a subsequent period their continuity from the central canal to the surface can no 
longer be recognized, although it is certain that even in the adult the cells which line 


the central canal and ventricles of the brain extend a long and indefinite distance into 
the grey matter. It is probable however that it is by transverse division of the 
spongioblasts, preceded by division of their nuclei, that the neuroglia-cells are origin- 
ally formed. At the same time it appears clear that although nerve-cells and 
neuroglia-cells are functionally very different, their origin is not so dissimilar as was 
at one time believed to be the case. It was taught formerly that the neuroglia is a 
form of connective tissue (which it resembles functionally), and it was supposed that 
its cells were developed from mesoblast, but of late years there has been much doubt 
cast upon its supposed mesoblastic origin, and the question is not yet fully decided. 
The researches of His have tended however to show that both the spongioblasts 
■from which the neuroglia-cells are believed to originate and the neuroblasts which 
give origin to the nerve-cells are both formed from the (at first undifferentiated) 
cells of the neural epiblast (see Embiyology, development of central nervous system). 
The investigations of Ramon y Cajal upon the development of these elements in the 
embryo chick and mammal further indicate that the distinction into spongioblasts 
and neuroblasts is not a fundamental one, for cells which from their shape and 
position would be classed amongst the spongioblasts of His may alter their character 
and by throwing out an axis-cylinder process become transformed into nerve-cells. 

Small concentrically striated globules, termed corpora amylacea, are frequently met with 
in the neuroglia of the cord in man, as well- as in many of the parts of the central nervous axis. 
They appear to be composed of proteid substance but, although long recognized, their mode 
of formation and their meaning are unknown. 


In transverse sections of the cord it is seen that the nerve-cells are not equally 
distributed throughout the grey substance, but are arranged in definite groups, 
which occupy nearly the same relative position in successive sections. The groups 
are therefore the sections of longitudinal tracts of grey matter rich in nerve- 
cells, and these tracts are named the ganglionic or ceU-columns of the grey matter. 
The longitudinal continuity of the groups can be seen in sections of the cord 
made parallel with its long axis and passing through the part of the grey matter 
where the groups occur. In such longitudinal sections it may also be observed that 
the cells tend, speaking generally, to be more extended parallel to the longitudinal 
axis of the cord the longer the segments of the cord, as indicated by the entering 
nerve-roots (Toldt). It may further be stated as a probable law, applicable at least 
to the cells belonging to the same group or column, that the longer the nerve-fibre 
which issues from a cell, the larger is the cell. Those segments of the cord 
from which the longest nerve-fibres issue by the anterior root have the largest 
anterior horn cells (Pierret). 

CeU-coluxiLn of anterior horn. — Of these groups or columnar tracts of nerve- 
cells, the one which is most constant and contains the largest cells is found along 
the whole of the ventral part of the anterior horn where the nerve-cells lie among 
the issuing fibres of the anterior roots. There seems to be no doubt that many of 
these anterior or motor nerve-fibres are directly continuous with the axis-cylinder 
processes of nerve-cells of this group. Hence it is sometimes named the moUn- 
cell-column, but it is more generally known as the cell-column of the anterior horn. 
Its cells are in most parts collected into two groups, a lateral or ventro-lateral 
(fig. 14, h) nearer the lateral column of white matter, and a mesial (a) nearer the 
anterior column ; in the cervical and lumbar enlargements there is a third, more 
deeply seated, dorsal or dorso-lateral group (&'). 

Of these several groups of cells into which the anterior honi cell-column is 
divisible, the one which is most constant along the whole length of the cord is the 



Fig. H.— Reciioicb or spiiull ooed id lowik okktical, kiij-domal, a 
Od tlie tight side of encb section tlie conducting Ira 


mesial group : on this account it is thought to give origin to the nerves which 
supply the dorsal muscles of the spinal column. It is sometimes described as 
forming two sub-groups, viz. : a dorso-mesial and a ventro-mesial. 

The ventro-lateral group probably gives origin to the nerves which supply the 
lateral and ventral muscles of the trunk, including the muscles of respiration. In 
the cervical region it is described as consisting of two parts, one more laterally 
situated, which gives origin to fibres of the spinal accessory, and another, more 
mesially placed, which is believed to give off the fibres of the phrenic nerva In 
the lumbar enlargement it also tends to be sub-divided. 

The dorso-lateral group is mainly developed in the cervical enlargement and 
lumbar enlargement, and has an evident relationship to the nerve-roots of the 
brachial and sacral plexuses. It also shows subordinate groupings, which probably 
have special connections with particular groups of the limb-muscles. For various 
conjectures regarding both these and other cell-groupings in the grey matter, the 
reader may consult the paper by Kaiser, which is given in the Bibliography. 

Some of the cells which are nearer the anterior commissure send their axis- 
cylinder processes through this commissure to the anterior white column of the 
other half of the cord : it is believed that these processes may be connected with 
nerve-fibres of the corresponding anterior root of the other side. 

In some of the lower vertebrates it may be made out that there are variations in the size 
of the oolomn of cells of the anterior horn in successive portions of the cord, the cells being' 
more numerous opposite the points of entrance of the nerve-roots, the attachment of which 
to the cord is in them more localized than in man and higher vertebrates. In this way some- 
what of a segmental formation of the column is indicated, and in some fishes and reptiles 
the enlargement of the group of cells and its enclosing grey matter is sufficiently marked to 
produce an external swelling opposite each nerve-pair. A similar segmentation is indicated in 
an early stage of development in all vertebrates, including man, by the fact that the cord is 
somewhat enlarged opiate each pair of nerve-roots. 

Clarke's column. — A second very well marked group or column of large cells, 
which occupies in transverse section an area at the inner or mesial angle of the base 
of the posterior horn (fig. 14,/), and appears cut off from the rest of the grey matter 
by a curved bundle of fibres derived from the posterior root, extends along the 
middle region of the cord from about the third lumbar to the seventh cervical 
nerve. This was termed by Lockhart Clarke the posterior vesicular column; 
it is usually known as Clarke's column, although the cells were first noticed by 
Stilling. It is best developed in the lower part of the dorsal (thoracic) region. 
From the fact that it is almost entirely confined to the thoracic region of the cord 
it was termed by Stilling the " dorsal nucleus." Bub although ceasing above and 
below the points mentioned, it is not altogether unrepresented in other parts, for 
groups of cells are found in a similar situation opposite the origin of the second and 
third sacral nerves (" sacral nucleus " of Stilling) and opposite the origin of the third 
and fourth cervical nerves (" cervical nucleus ") ; and elsewhere there are scattered 
cells of the same character in the same part of the section of the cord. The cells of 
this column, like most, if not all, the cells of the spinal cord^ are multipolar, and 
their axis-cylinder processes tend towards the lateral column, where they are believed 
to form the direct cerebellar tract (Flechsig). The cells themselves are surrounded 
by a fine plexus of nerve-fibrils, probably derived from collaterals of the posterior 
root-fibres. They are of large size, measuring, according to Mott, in their longest 
diameter, which is directed longitudinally, from 40/i to DO/i, the largest being found 
in the lowermost part of the column. In the foetus and even in the new-bom child 
they are much smaller (25/i to SO/Li), but by the second or third year after birth 
they have nearly attained the same size as in the adult. 

Lateral cell-coliuiin. — A third column of cells lies in the intermedio-lateral 


tract (lateral cell-column, fig. 14, d). Like that tract, the ganglionic column it 
contains chiefly appears as a distinct formation in the thoracic region ; in other parts 
the cells do not form so distinct a grgup, but they appear nevertheless to be repre- 
sented to some extent along the whole cord. Its cells are bipolar or multipolar, and 
measure .on an average JJO/i in diameter, being considerably smaller than those of 
Clarke's column or those of the anterior horn. In the upper part of the cervical 
region a group of cells becomes distinct in a similar situation (lateral nucleus), and 
is traversed by the roots of the spinal accessory nerve. 

Middle cell-coluiim (Waldeyer). — This is formed of what in sections of the 
cord forms an ill-defined group of moderately-sized cells placed in the middle of the 
grey matter of the crescent. The cells are most distinct as a group in the cervical 
region, and also more numerous there, becoming fewer in number as Clarke's column 
becomes more evident. In the dorsal region they lie mostly at the side of Clarke's 
column, but further down they again move nearer the middle of the crescent. They 
are distinguishable right down into the sacral region. It is not known with what 
fibres they are connected, but fibres from the postero-lateral columns course amongst 
them, and it may be that, on the other hand, they give off nerve-processes to one of 
the conducting tracts ( ? to the antero-lateral ascending tract). They stain less 
deeply with carmine than those of the motor column or of Clarke's column. 

Cells of posterior horn ; solitary cells. — The cells of the posterior horn 
are not grouped very definitely, but for purposes of description they may be roughly 
sub-divided into — 1, those at the base of the horn ; 2, those near the middle of the 
horn ; 3, those at the margins ; and 4, those of the gelatinous substance of Rolando. 
They vary in size, some of the largest being found near the mesial margin of the 
horn ; these often have a characteristic long curved process (comet-cell, Waldeyer) : 
and even within the same group both large and small cells may be found intermixed. 

But in addition to the groups, a number of scattered cells are met with, dis- 
tributed through the posterior horn. These cells vary much in form and size, but 
are for the most part spindle-shaped. They are usually spoken of as the solitary 
cells. The axis-cylinder processes both from some of these cells and from cells of the 
lateral cell-column pass towards the anterior horn and also towards the anterior 
commissure, and they are believed to give origin to the smaller fibres which issue 
with the anterior roots. Some of the axis-cylinder processes of these cells do not 
however leave the grey matter but are branched and their ramifications lose them- 
selves in the interlacement of fibrils which invests other cells. In the lamprey it has 
been shown by Freud that cells which appear to correspond with the solitary cells 
send their axis-cylinders into the posterior roots, and more than one observer has 
described a direct passage of the axis-cylinder process of one of the more deeply 
lying cells of the anterior horn through the grey matter into the posterior root, and 
thence past the ganglion into the mixed nerve without coming into connexion 
with any of the ganglion-cells. 

The cells of the substance of Rolando were first noticed by Gierke. They are 
small round granule-like cells, closely packed and staining with difficulty. They 
appear to have been often taken for neuroglia cells, but, according to Gierke and 
H. Virchow, there is little doubt about their nervous nature. 

Cells are occasionally found separated from the general mass of grey matter and 
lying out amongst the fibres of the white columns. These ** outlying cells " have 
been described by Stilling and others, recently in detail by Sherrington. 

It has been shown by Golg^i that the nerve-cells of the central nervous system may be 
primarily classified nnder two heads, viz., 1, those with a lon^ axis-cylinder process which 
becomes a medollated nerve-fibre ; and 2, those with a short axis-cylinder process which may 
or may not become meduUated, and soon ramifies and loses itself in neighbouring parts of 
the grey matter. Grolgi is of opinion that the former are to be looked upon as "motor or 




efferent " celU. and tbe latter as " senroiy or afferent." bat it is doubtful if thii phTsiolo^cal 
distinctioa will hold good. la the spinal cord the calls of the anterior horn, those of 
Clarke's column, and man; of the cells of the lateral cell-colamn and of the posterior horn 
belonjf to the first category, while many of the solitary celbi, the small calls of the sabstance 
of Rotanilo. and nome of those of the lateral cell-colnmn, belonir to the latter. 

A, from a child of six. Magnified 150 diameters. A', some of the ciliated cells, highly magnified. 

B, section of the isthmua from the lumbar cord of an adult (nt. 33), showing tha Gentnl canal in the 
middle sarrODoded by the substantia geUtinoBa centralis, /.a., anterior median fissure; p.m.c, 
pceterior white column ; a,c., anterior wliite cpmmisaure. Magnified 30 diameters. 

Commiainrac — The aut«iior oommi«mre (Qg. 15, B, ax.) coDsiats uf medul- 
lated nerve-fibreB which pass on each side, some into the anterior white colamn, 
others into the anterior horn of gre^ matter. Their course is not strictly tranaverBe, 
manj fibrea ivhich enter the ventral part of the commissare at one aide leave it at 
the dorsal portion on the other side. There is tbns an oblique deoussatioD at the 
middle line (fig. 15). This decusaation is moat distinctly seen in the comparatively 
short and wide commisanre of the Inmbar region, and in the upper part of the cervical 
region. In tbe latter sitnatiou it appears as a continuation of the decussation of the 
pyramids of the medulla oblongata, to be afterwards described. In addition to the 
transverse there are a few longitndinnl bundles of hbres in the region of this commis- 
sure. The fibres are often somewhat displaced by vessels which pass into the grey 
substance from the anterior fissure. 

The pcwterior omnndMrnnx* also contains medullated fibres running trans- 
versely or with a slight obliquity, but there is a large amount of neuroglia between 
them, and this gives the commi^sui'e a grey aspect. In this commissure is 
contained the central canal of the spinal cord surrounded by an area free from 
medullated nerve-fibres, and occupied by a substance which, like the superficial 
neuroglia and the substance of Rolando, has in tbe hardened condition a reticulated 
structure and in the fresh state a gelatinous aspect. It is termed subttanUagilatmoaa 


centralis. In this gelatinons substance man; of the fibres of the poaterior com- 
missure appear to end (see fig, 15, B). There is rather more of the posterior com- 
missnre behind the central canal than in front. The fibres of the posterior pare curve 
backwards on reachinji; the crescents of grey matter and pass towards the bundles of 
the posterior roots, whereas the rest divei^e at various angles into the crescent. 

The oestnd canal is lined with a layer of ciliated epithelium (,fig. 15, A, A'). 
Each cell is provided with a bunch of cilia on the side which is turned towards the 

Kg. IS, — DuoftiM TO i: 
or iHE wHin coLDHiis or thk spinal cord to thk kervi-(!K[.i,9 is THM OHEV MATTKB. (B.A.S.) 

lumen of the canal : the other end of the cell is prolonged into the reticular 
substance just mentioned, and there becomes lost to view. 

In the adult human subject the lumen of the central canal is not unfreqnently 
obliterated, being filled up by detached cells. 

oBiant or thz bfinal niirtxb. 

The roots of tfae spinal nerves are attached along the sideM of the cord, opposite 
to the corresponding horns of the grey matter ; the posterior roots entering along a 
straight line at the poatero-lateral groove, and the untcrior roots being scattered 
somewhat insularly upon the surface (hg. 7, b). 

The antsrioz rooti are seen in a transverse section to pass through the white 
substance and to ent«r the greycornn in several buudlei^, which have a slight upward 
inclination, so as to be often cut obliquely if the section be exactly in a transverm 
plane. Some of the fibres on reaching the grey matter are directly connected with 
the axis-cylinder processes of the large nerve-cells of the coma. Others pass by 
the cells without, so far as can be seen, entering immediately into relation with 

As soon as the handles enter the grey matter, their fibi-es diverge from one 
another, some passing mesially, others laterally, and others straight backwards (fig. 16). 
Of those which pass mesially some are continued into the axis-cylinder processes of 


the mesial group of cella of the anterior coma, and others to the other aide of the 
cord through the anterior commlBenre, there perhaps to become connected with the 
corresponding cells. The outwardly directed fibres of the root are connected with 
the cells which form the lateral gronpa of the anterior honi, and partly with some 
of the cells of the intermediate cell-column. The middle fibres are partly con- 
nected to the cells of the anterior horn, and partly pass on to the posterior 
horn, where they are probably continued into some of the cells there present. 

In tile cervical region of the cord, from the aizth nerre npwards, the root-Obres of the 
epinal part of the Bpinal acceiuiorj nerve ma; also be Been pasaing oat of the anterior hom 
thfongh the lateral column (fig. 31, p. 40). Thej arise from a group of somewhat large cells, 
which in the uppermost region of the cord lies in the antero-lateral part of the hom. close to 

I OoLQi'a HKTHOD (Bam6n ; Cajtd). 

A , siu-cylindera of antarior root-Gbrea isiuiiig from large cells of the anterior hom, C. 

B, Posterior root-fibres pasting fram the bipolar cells of the spinal ganglioD, into the posterior column 
of tlis spinsl cord, B, nhere thej bifurcate, d, and become loiigitudiual ; e, /, g, collaterals from these 
Gbrea, poaaing into the graj matter. 

its Tentral edge, but in the middle and lower cervical regions tends gradually to oconp^ a 
position nearer the base of the hom (see p. 16). This group of cells is the direct continnatiou 
dowDwards of the acceesoiy nucleus which will be seen in the lower part of the mednlla 

The posterior roots at their entrance into the cord are seen to separate into 
two sets. Of these the lateral, which contains most of the smallest fibres of the 
root, enters opposite the tip of the posterior born and joins a bundle of fine longitu- 
dinal fibres which lies close to the periphery of the cord in this situation. This bundle 
is known as the inarginal bundle or column of Lissau^. Its fibres, which are 
evidently different from most of those which enter with the posterior root, for they 
acquire their medullary sheath considerably later (Bechterew), appear, as they pass 
Tertically, gradually to lose themselves in the adjacent gelatinous subftance. The mesial 
set containing the larger and some smaller fibres of the posterior rout passes into the 


postero-lateral white column, with the longitadi- 
nal fibres of which ita fibres become continuons ; 
from this column man; of them sweep with 
bold curves into the adjacent grej matter. At 
their entrance into the cord their direction hke 
that of the bundles of fibres of the anterior roots 
is in most regions of the cord obliquely upwards. 


INCDBITIOE (Ram6n ; C&jnl). 

Tbii ligare sbowg the coaise of 6 eat«tiiig fibres of tfae 
poiterior root and Bome of tha loDgitudiiutl fibres of tbe 
{i«l«riar colunii]. 

A, A, fibres of the posterior root ; B, bifnrcatjoa of 
one of them iu form of s T; G. D, origin of collateral 
bianthm ; E, fibres of QoU's trac;t. eiao giving off colU- 

Collatsral BbrtM of the portarior roots 
and of th« white oolnmiui.— It has been 
definitely shown by Ramon y Cajal, whose 
researches into this subject have been confirmed 
by Kiilliker and v. Gehuchten, that the fibres of 
the posterior roots as they enter the cord join by 
a Y- or X-sf>*pe<i junction with longitudinal 
fibres of tbe posterior column ; in other words 
that they bifurcate as they enter the cord into 
two principal branches which run upwards and 
downwards in the posterior white column or in 
the adjacent part of the posterior cornn. It 
has also been proved by the same observers 


This figure shows cotUteials passing into the grey matter from nil the white Golnnins of the card. 
The; are seen to form an eBpeciall; close plexus in the posterior bom, jost within the subaluiRe of 
Bolanda, and in tbe poaurior eommissure. 
c, central canal ; v, anterior and d, posterior surface of tbe cord ; p, p, posterior roots. 


that both from the root-fibre before its biiiircation and from its ascending and 
descending stems there are given oflF at tolerably frequent intervals "collateral" 
branches which are directed inwards towards the grey matter; into which they 
penetrate for a variable distance and within which they ultimately end by breaking 
up into a ramification of nerve-fibrils which may frequently be seen to have a close 
relationship to cells of the grey matter. In this way collateral fibres are given off 
from the posterior root-fibres and from their longitudinal extensions, some of which 
penetrate as far as the anterior horn of the same side, others pass through the 
posterior commissure into the gi*ey matter of the opposite side, others towards the 
lateral horn and intermediate cell-column, whilst others do not extend beyond the 
posterior horn, passing towards Clarke's column or the solitary cells of the crescent, 
while many end in or near the substance of Rolando. These collateral fibres can 
be seen in sections of the embryonic cord which have been prepared by Golgi's 
method, to pass into the grey matter in large numbers from the posterior colunms, 
most of the fibres of which are in fact prolongations of posterior roots which 
have entered the cord. But they are by no means confined to the fibres of the 
posterior columns, for from all the longitudinal white columns of the oord the 
same convergence of collateral fibres into the gi'ey matter can be seen (see figs. 16 
to 20). 

The passage of coUateral fibres into the grey matter from the white columns of the oord 
was first noticed by Golgri^ who stated that the fibres of the anterior roots also give off in their 
passage towards the surface of the cord fine lateral ramuscles which become lost in the adja- 
cent nervous matter. Other observers have for the most part failed to detect these collaterals 
of the anterior root-fibren. 


It is impossible mechanically to unravel the tracts of nerve-fibres in their passage 
along the spinal cord, and it is exceedingly difficult to trace the same fibre or fibres 
for any distance in microscopical sections of the organ. But the task of following 
out the course of certain sets of fibres has been much facilitated of late years by the 
application to the subject of certain special developmental and pathological methods 
of , observation. Thus it is found that if the development of the spinal cord is 
carefully observed, the medullary substance of the nerve-fibres is formed later along 
certain tracts of the white columns than in the rest of the white matter, appearing 
first in those tracts which are the immediate prolongations of peripheral nerves, and 
being longest delayed in those which are connected with the higher centres in the 
brain, so that in transverse sections of the cord these non-medullated tracts are easily 
distinguishable by their more transparent grey appearance and by their different 
behaviour with staining fluids (Flechsig). 

The following list (from Kahler) gives the order of formation of the myelin-sheath in 
the several tracts of the cord : — 1. Fibres in anterior column derived from anterior roots. 
2. Postero-lateral column (its posterior part somewhat later than its anterior part). 3. The 
lateral column near grey matter (the anterior X)art first, then the narrow posterior part between 
pyramidal tract and posterior horn). 4. Postero-mesial column. 5. Direct cerebeUar tract. 
6. Antero-lateral ascending tract. 7. Pyramidal tracts (shortly before birth). 

Another method by which similar results are arrived at consists in tracing the 
course which the degeneration of the fibres pursues in consequence of a lesion either 
in the encephalon, or in the spinal cord itself, or even in the peripheral nerves ; the 
lesions being produced by accidental injury, by pathological changes, or experimen- 
tally in animals. The degenerations which follow are either the result of the 
Wallerian law that separation of a nerve-fibre from the nerve-cell with which it is 
connected and from which it has grown out is followed by degenerative changes in 



Fig. .20. — DlAGBAM 8H0W1KG THK PKU- 

1, a cell of the cortex cerebri ; 2, its 
aziB-cylinder or nenre-process passing 
down in the pyramidal tract, and giving 
off collaterals, some of which, 3, 3, end 
in arborisations around cells of the ante- 
rior horn of the spinal cord, the main 
fibre having a similar ending at 4 ; coll., 
a collateral passing in the corpus cailosuni 
to the cortex of the opposite side ; «£r., a 
collateral passing into the corpus stria- 
tum ; 5, axis-cylinder process of anterior coniu-cell passing to form a terminal arborisation in the end- 
plate of a muscle- fibre, m. 

6, a cell of one of the spinal ganglia. Its axis-cylinder process bifurcates, and one branch, 7, passes 
to the periphery to end in an arborisation in the sensory surface, «. The other (central) branch bifurcates 
after entering the cord (at 8), and its divisions pass upwards and downwards (the latter for a short 
distance only) ; 9, ending of the descending branch in a terminal arborisation around a cell of the 
posterior horn, the axis-cylinder process of which, again, ends in a similar arborisation around a cell of 
the anterior horn ; 10, a collateral passing from the ascending division directly to envelop a cell of the 
anterior horn ; 11, one passing to envelop a cell of Clarke's column ; 12, a collateral having connections 
like those of 9 ; 13, ending of the ascending division of the posterior root-fibre around one of the cells of 
the posterior columns of the bulb ; 14, 14, axis-cylinder processes of cells of the posterior horn passing 
to form an arborisation around the motor cells ; 15, a fibro of the ascending cerebellar tract passing up 
to form an arborisation around a cell of the cerebellum ; 16, axis-cylinder process of this cell passing 
down the bulb and cord, and giving off collaterals to envelop the cells of the anterior horn ; 17, axis- 
cylinder process of one of the cells of the posterior column of the bulb passing as a fibre of the fillet to 
the oerebmm, and forming a terminal arborisation around one of the smaller cerebral cells ; 18, -axis- 
cylinder process of this cell, forming an arborisation around the pyramidal-cell, 1. 


the part of the fibre thus separated from that centre {secondary degeneraUona), or they 
may follow from the prolonged disuse of a nervous tract, especially in young animals, 
as when a limb has been removed or from some other cause (teitiary degenerations). 
The degeneration which follows a lesion of part of the nervous centre, and especially 
section of the spinal cord, is in some tracts above the lesion, in which case the 
degenerated tract is styled "ascending," in others below ("descending") (see also 
p. 27). The place of the degenerated nervous substance is ultimately taken by a 
non-nervous fibrillar tissue, which, by its difference of behaviour to staining fluids, 
can easily be distinguished from the surrounding undegenerated white substance 
(stage of sclerosis). In new-born and young animals, after a longer interval, groups 
of nerve-cells are affected by the degenerative processes, and the cells may even 
eventaally disappear altogether (v. Gudden). When this is the case it may be 
assumed that they are in connection with the fibres which have been cut ; these 
being probably the axis-cylinder processes of the cells. 

Thus in a rabbit in which immediately after birth the sciatic trunk is resected^ when the 
animal is fnll-grown the corresponding anterior comoal cells are found to have become 
atrophied, and similar results are obtained with motor nerves generally, both spinal and 
cranial (v. Gudden, Forel, Ganser, Mayser). 

Tracts of the antero-lateral column. — Several tracts can by these methods 
be traced in the antero-lateral column, not only along a great part of the spinal cord, 
but into or from certain parts of the encephalon. The long tracts in this column 
are the direct and crossed pyramidal {descending)^ the antero-lateral or veniro-lateral 
ascending, the antero-lateral or ventro-lateral descending, and the dorso-lateral 
ascending (or direct cerebellar). 

Descending tracts in tlie antero-lateral colnmn. — The pyramidal tract 
is directly traceable down from the opposite pyramid of the medulla oblongata, and 
ultimately from the cerebral cortex (Rolandic region). The gieater number of the 
fibres which compose the pyramid cross at the upper limit of the spinal cord, down 
which they pass in the posterior part of the lateral column as a compact bundle of 
fibres occupying in transverse section a somewhat triangular area, which lies in the 
angle between the posterior horn and the outer surface of the cord, but is in most 
parts separated from both by fibres belonging to other systems. This lateral or 
crossed part of tfie pyramidal tract (figs. 14 and 24), can be traced as far as the third or 
fourth pair of sacral nerves, becoming gradually smaller below and approaching the 
surfece of the cord. 

A few fibres of the pyramidal tract are found scattered in other parts of the 
antero-lateral column. 

Some of the fibres of the pyramids of the medulla oblongata do not decussate at the 
upper limit of the cord. These pass down close to the anterior median fissure, forming 
the anterior or direct portion of the pyramidal tract (fig. 14) {column of Tiirck), which 
gradually diminishes as it is traced downwards, and usually ceases altogether at 
about the middle of the dorsal region of the cord. It is probable that the decus- 
sation of these anterior pyramidal tracts goes on along their whole course, their 
fibres passing through the anterior commissure and through the grey matter of the 
opposite side to reach the lateral pyramidal tract on the other side of the cord. 

There is much variation in the development of the anteiior pyramidal tracts in different 
individuals. In some they are so well marked as to form a visible prominence on the surfaoe 
of the cord close to the anterior median fissure and separated from the rest of the anterior 
solumn by a groove, the anterior inferm-ediafe sulcus of Rauber. In others they are quite small, 
■or may even fail altogether. In this case it may be assumed that the decussation of the pyra- 
mids, which is known to be subject to considerable variation, has been more complete than 
usual. In other cases again the anterior pyramidal toicts may be unsymmetrical, bein^r 


more developed on one side than on the other, or the tract on one side may he wholly unde- 
Teloped. The direct tract is said to be wanting in 15 per cent, of cases in man. In different 
animals there is also much variation in the position and size of the pyramidal tracts. A 
well-marked direct pyramidal tract appears to be absent in most animals, even in monkeys. 
In some (mouse, rat, g^inea-pigr) the pyramidal tracts are in the posterior columns, but in 
most animals (rabbit, cat, dog) they run' in the lateral columns as in man. The fibres of the 
pyramidal tract are probably connected with the anterior horn by collateral fibres, which ramify 
amongst the large cells that give origin to the anterior nerve-roots (figs. 16, 20). 

The pyramidal tracts are undoubtedly the paths by which voluntary impulses pass from 
the brain to the vai'ious spinal segments. All the fibres within the area embraced by the 
" tract " are not, however, of the same nature, although fibres of the one function predominate : - 
and this is probably coiTect of all the so-called *' tracts " of conduction* 

There are at least two descending tracts in the antero-lateral column, besides the 
direct and crossed pyramidal. One, the antero-lateral descending cerebellar 
tract (anterior marginal bundle of Loewenthal), consists of fibres which are connected 
with cells in the cerebellar cortex of the same side, and which undergo degeneration 
on removal of the corresponding half of the cerebellum (Marchi). These fibres form 
an extensive circumferential tract in the anterior three-fourths of the antero-lateral 
colamn, spreading inwards in front of the crossed pyramidal tract to reach the 
intermedio-lateral tract of the grey matter. The tract which is thus marked out 
(see fig. 26, p. 552) embraces (in the dog) the part of the anterior column which 
in man is occupied by the direct pyramidal tract, and also the whole region of the 
tract of Gowera (see below), the fibres of these two tracts being intermingled. Some 
of the fibres of the anterior roots also exhibit degeneration after removal of the 
cerebellar hemisphere, and are therefore probably directly continued from fibres of 
this tract. 

In the monkey a few fibres in this column degenerate after lesions of the cerebral 
hemisphere of the opposite side. They are intermingled with those of the descending 
cerebellar tract and with those of the tract of Gowers, and are connected with cells, 
in the Rolaudic region of the cerebral cortex, as shown by the fact that they 
degenerate after lesions of that region. These fibres may perhaps be regarded as 
belonging to the system of the direct pyramidal tract, which in the monkey does 
not exist as a well-marked tract as in man : it has not yet been ascertained whether 
they occur in man as well as the direct pyramidal. 

Ascending tracts in the antero-lateral colnmn. — The dorsclateral 
ascending cerebellar tract {direct lateral cerebellar tract of Flechsig) (fig. 14) lies 
between the lateral pyramidal tract and the outer surface of the cord, occupying a 
somewhat narrow area of the transverse section, which in the upper regions of the 
cord reaches to the tip of the posterior horn, but lower down becomes more limited, 
and is separated from the horn by the intervention of the adjoining pyramidal tract. 
It begins to appear at the lower dorsal region in man, and is then seen in all sections 
of the cord and lower part of the bulb, passing eventually by the restiform body 
into the cerebellum (middle lobe) (see fig. 27, p. 33). 

It is found that there are a few fibres scattered through the neighbouring parts 
of the lateral column which, from their development simultaneously with those of 
the cerebellar tract, should be apparently reckoned with it. The axis-cylinder 
processes of the cells of Clarke's column are said to give origin to the fibres of the 
dorso-lateral cerebellar tract. The fibres of this tract acquire their medullary sheath 
somewhat earlier than those of the pyramidal tract. They are also considerably 

The ventro-lateral or antero-lateral ascending cerebellar tract {antei'O- 
lateral ascending tract of Gowers) occupies a position in the sectional area of the 
lateral column which is anterior or ventral to the dorso-lateral cerebellar tract, and 
it has in section an arched shape curving from immediately in front of the crossed 


pyramidal tract (where it is most strongly marked) round the superficial part of the 
lateral column in front of the dorso-lateral cerebellar tract, and tailing off gradually 
between the issuing anterior roots to reach the anterior column. It can be traced 
upwards into the medulla oblongata and pons Varolii (fig. 27), and eventually enters 
the cerebellum along with the superior peduncle, passing mainly to the vermis. It is 
uncertain from what cells the axis-cylinders of its constituent fibres spring, but it 
is probable that they arise from some of the cells of the posterior horn. Its fibres 
are intermingled with those of the descending cerebellar tract. 

The remainder of the antero-lateral column which is not comprised in the above 
tracts encircles the anterior comu ; it is termed the antero-lateral gronnd-bimdle. 
It varies in sectional area with the size of the nerve-roots and of the grey matter, 
and many of its fibres not improbably are of a commissural nature, serving to 
connect the grey matter of different segments of the cord. It receives fibres also 
from the grey matter of the other side through the anterior commissure (fig. 15, B, 
fl.c), and is in part composed of fibres of the anterior roots which course for a 
certain distance obliquely within it before leaving the cord. Many intersegmental 
fibres also occur scattered amongst the fibres of the long tracts. 

Tract of Lissauer. — At the posterior part of the lateral column, close to the 
entering fibres of the posterior roots and directly derived from them, there i^ 
constantly to be seen a well-marked bundle of fine nerve-fibres, which was first 
described by Lissauer, and since by Bechterew and others. It is not always confined 
to the lateral column, but may extend into the postero-lateral column. 

Tracts of the posterior white column. — This column is mainly composed 
of two long ascending tracts, viz., the tract of GoH, which about corresponds with 
the postero-mesial column, and the tract of Burdock, which embraces the remainder 
of the posterior column. In the lower part of the cord these two tracts are not 
marked off from one another in the adult, but from the middle of the dorsal region 
upwards the postero-mesial column is separated from the postero-lateral by a septum 
of pia mater. Qf the two parts of the posterior column the tract of Bnrdach is 
mainly composed of rather large fibres which are joined by, i.e., are continuous with, 
the large fibres of the entering posterior roots. After a certain course, in which they 
give off numerous collaterals to the grey matter, they appear to enter the grey matter 
and to come into intimate relationship^ although not into actual continuity, with its 
cells, especially those of Clarke's column. The fibres of the tract of OoU, on the 
other hand, are for the most part of smaller diameter. They also are derived from 
posterior root-fibres, but instead of soon entering the grey matter of the cord many 
of them run up the postero-mesial column into the medulla oblongata, where they 
terminate amongst the cells of the nucleus gracilis. 

The colnmn of Groll in the embryo shows a dlBtinction into two parts, one mesial, olose to 
the posterior median fissure, and a dorso-lateral part, lying near the dorsal surfaoe of the coid 

Descending fibres of the posterior colnmn. — In the middle of the 
sectional area of the postero-lateral column a few fibres are constantly found, 
which undergo descending degeneration after lesions of the cord. These are often 
described as constituting a special tract ('' comma '' tract), but they are a good deal 
intermingled with fibres of the adjacent ascending tracts. Whether they originate 
from cells higher up in the cord or are derived from the descending branches 
of the posterior root-fibres is uncertain. The latter, it may be remembered, extend 
a certain distance down the cord from the Y-shaped division of those fibres, giving 
ofi^ collaterals to the grey matter, and ultimately themselves turning into the grey 
matter. The extent to which these descending branches of the posterior roots may 
pass down the cord has not as yet been determined. 



It necessarily results from the Wallerian law of degeneration of nerve-fibres 
(Vol. I., p. 356) that every lesion of the nervous system in which fibres are cut or 
crushed must be followed by degeneration of nerve-fibres either above or below the 
lesion according to the position of the cells from which the fibres have originally 
grown, and which serve throughout life to maintain the nutrition of the fibres wiUi 
which they are connected. Any such degeneration which occurs above the lesion is 
usually termed " ascending," and below the lesion " descending." 

These terms must not be taken to imply, as is erroneously done by some authors, either that 
the degeneration starts from the lesion and extends upwards or downwards along the fibres, 
or that the nerroufl impulses which the fibres conduct necessarily have an ascending or a 
descending direction. For it is known (1) that the degeneration in the peripheral part of a 
cut nerve-fibre occurs simultaneously along its whole course ; (2) that a nerre-fibre may 
undergo " desoending *' degeneration, although it normally conveys ascending impulses, e^f., 
the peripheral afferent nerves. 

Since the terms ascending and d^cending as applied to nerve-degeneration lead to much 
confusion of ideas it would be better, if possible, to discard them and to adopt words which 
merely imply that the degenerative process occurs above or below a lesion. But unfortunately 
those terms have taken such deep root in the literature of the subject that this course 
would be very difficult, and might lead to even worse confusion than their retention. 

Similarly, if the nerve-cells from which the fibres are thus derived are removed 
or destroyed, the fibres, with any branches which they may give oflF, will degenerate 
along their whole course. Hence any tracts of fibres in the spinal cord which are 
derived from cells in parts of the brain, degenerate on destruction of those parts. 
Further, those fibres which have grown into the spinal cord or brain from nerve-cells 
situated external to those organs (e.g., the fibres of posterior roots of spinal nerves and 
corresponding fibres of cranial nerves) will, if cut between the spinal cord or brain 
and the ganglion-cells from which they are derived, undergo degeneration from the 
point of section, not only as far as the surface of the central organ, but also along 
their whole course within that organ, and the degenerative process ^ill include all 
their branches. Thus much having been said to explain the meaning of the results 
which are obtained by the study of nerve-degenerations, we may proceed to consider 
the degenerations which occur within the spinal cord : (1) from section of the pos- 
terior roots of the nerves ; (2) from lesion or removal of parts of the brain ; (3) from 
section or other lesion of the spinal cord itself. 

1. Degeneratioiis resulting from section of the posterior roots. — These 
have been investigated in the dog by Singer and Kahler, in the monkey by Mott 
and Tooth. It is convenient in describing the effect of sections of the posterior 
nerve-roots to consider them in the sacro-lumbar and in the dorso-cervical regions 
respectively, although the course of the degenerative process is essentially similar in 

(a,) Section of the jposterior roots of the sacro-lumbar nerves. — This has been 
most satisfactorily investigated by Singer in the dog and by Mott in the monkey. 
Section of these nerves, e.g,, of the whole cauda equina, is followed by '* ascending " 
degeneration in the posterior column of the same side along the whole length of the 
spinal cord and as far as the nucleus gracilis of the medulla oblongata. But the 
degeneration does not occupy the same position and extent in every part of the 
cord. At the lowest part it involves the whole of the posterior column (fig. 21, a), 
but as soon as a point is reached at which uncut nerve-fibres enter the cord, these 
now occupy the part of the column nearest the horn of grey matter, while degenerated 
fibres are seen in that part only which is nearest the posterior median fissure {b). 



In this gitnation thej pass np the cord, diminighinj; in nnmber, at firet rapidly and 
^tervards more slowly, nntil at length a reUtivelr small tract of de^nenition is 
foand, occapying the postero-niesial angle of (Soil's tract, in which it rnns to the 
nncleus gracilis {fig. 21, r). 

(6.) Section of the posterior roots of the dorsal and eertncal nerves. — After section 
of one or more of these roots degeneration oocnrs immediately above the section in 
the part of the postero-lateral column nhich is next to the posterior horn (figs. 22, 
33, a). Komewbat higher np this becomes separated from the horn by other nncut (and 
therefore uiidegeDerated)neiTe-root-fibres,and approaches the poetero- mesial colnmn. 
Still higher it is foand to have reached that column, where it is represented by asmaller 

HI l»a. (Kahler.) 

a, at tbe levcJ of Ibe Gist thonuiic ; h, at the siitli cenrical ; c, at the Grat cervical. 
(Pig>. 21, 22, and 23 are copied from Toldt'a " OeveUlebre.") 

tract of degeneration, which in section lies ubliqnely across the column. With 
regard to this degeueration in tbe postero-mesial column it is to be noted that while 
that which results from section of the lower (Itimbu- sacral) roots occupies in the 
higher parts of the cord the postero- median angle, as above described, the degene- 
ration resulting from section of dortal roots lies next to this, that resulting from 
section of lower cervical roots passes up Goll's column in its lateral part next 
to the column of Burdach, and finally that resulting from section of npper cervical 
roots is confined to Burdach's column, and ends in the nucleus cuneatus of the 
medulla oblongata. In other words, the lower the root the more mesial is the 
resnlting long degeneration in the higher parts of the cord and in the medulla 
oblongata. The fibres, as they enter the cord with the posterior nerve-roots, form 


in fact a snccession of lamellar titicts, which lie in each case at first next to the 
posterior comu, and become gradually shifted medianwards by those which enter 
the cord with the higher nerve-roots. 

It is fmHiher to be noted that in all cases the degeneration falls off 
markedly in amonnt as we trace it np the cord, and that what remains is 
eventually confined to a part of the posterior column which contains normally 
fine or medium-sized fibres only. From this it may be inferred that the larger 
fibres of the posterior roots — which in fact form the bulk of those roots — have 
a relatively limited course after entering the cord. They probably end by their 
collateral branches, and ultimately by their main ascending branches, turning into 
the grey matter and breaking up into terminal ramifications in the fine interlacements 
of nerve-fibrils which occur in the neighbourhood of the nerve-cells and cell-groups. 
These terminal branches and the nerve-fibrils which result from their ramifications, 
should also, of course, from the Wallerian law, degenerate after section of the roots, and 
there is no doubt that they actually do so, although from their scattered course in 
the grey matter it is difficult to prove the fact. It has, however, been shown by 
Mott that after section of the lower posterior roots, the fine nervous interlacement 
which surrounds the cells of Clarke's column disappears for some little distance 
above the entrance of the cut nerve-roots, and it may therefore be fairly inferred 
that some of the fibres of the posterior roots give origin directly and by collaterals 
to this interlacement. Others, probably, are similarly related to other cells, both in 
the posterior and anterior horns of the same side, and even on the other side of 
the cord, for it will be remembered that ramifying collaterals can be traced from the 
posterior root-fibi'es to all these parts (see figs. 16 and "20), Thus all the larger and 
some of the smaller * fibres of the posterior roots gradually end as they are prolonged 
up the cord, until finally only those remain which pass up the postero- mesial 
column towards the medulla oblongata. Even these become gradually diminished 
in number, no doubt from the fact that some of them terminate in the grey matter 
as they proceed. 

It will further be remembered that the fibres of the posterior roots divide on 
their entrance into the cord into two main longitudinal branches, ascending and 
descending. Of these the ascending only has been traced by the above degenerations, 
but the descending branch must also undergo degeneration. It is, however, not 
easy to trace out its course. The only known "descending" degeneration in the 
posterior columns is along the narrow curved tract in the postero-lateral column 
which is known as the "comma,'' but would be better termed the posterior 
descending tract. Mott has found that this degeneration results not only in sections 
of the cord, but also after section of posterior nerve-roots, and that it has a 
limited extent, one or two centimeters only. It is therefore not improbable that 
this degeneration may represent the descending branches of the cut posterior root- 
fibres (cf. p. 26, and fig. 20, 8 to 9). 

It will be conyenient here to sum up what is known or may be inferred aa to the course 
of the fibres of the posterior roots within the oord as determined by anatomical, embryological 
and experimental (degenerative) methods. (1.) Each fibre on entering the oord divides into 
an ascending and a descending branch, which form the longitudinal fibres of the posterior 
column. Both from the root-fibre before division and from the branches, collaterals come off 
which lose themselves in terminal ramifications enveloping nerve-cells in the grey matter. 
Probably also after a longer or shorter course the main branches terminate by passing in like 
manner into the grey matter. (2.) From each root on entermg the cord a lateral bundle of 
small fibres (Lissauer^s bundle) is given off, which lies partly lateral and partly mesial to 
the apex comu posterioris, while the remainder of the root forms a large lamellar bundle of 
mixed large and small fibres which run longitudinally in the postero-lateral column close 
to the comu of grey matter. (3.) From thi8 lamellar bundle many fibres pass upward 

' Thoee of Lisfauer's bundle. 



along the wbole length of the cord, being graduallj shifted iawonl tonarda the p 
menal colniDn, and forming as tbey reach thie colunm the t[«ct of GoU, whiob becomes the 
fnnicnluB ffracilis in the medulla, oblonjrata ; from the tract of GoU the fibres eventaallj 
pasB, Bome into the prey matter of the upper part of the spinal cord, others into grey matter 
in the nacleos gracilis of the bulb, whilst yet others derived from the appermost 
cerrical roots do not reach the tract of Goll but pass np to the bulb in the fnnioulna ciinaatiis 
and end in its oiicletia. (4) The remainder of the flbrea which have entered by the 

Corp. (juadr. ant 


degenerated fibres ai 

The degeneration is mainly on the lame side in the mesenceplLalon, jions, and bulb, bnt on the 
oppwile aide in the spinal cord, A few fibres are degenerated in the antero-Iateial region in the card, 
but the degeneratian is otherwine confined to the pynuaidal tracts. 


posterior roots have only a limited coarse up the postero-lateral column, passing, as they 
ascend, into the grey matter, in which they and their collaterals form the fine nervous 
plexus around many of the nerve-cells which has been already mentioned. From some of 
the largre fibres the plexus around the cells of Clarke's column (and perhaps also around 
the cells of the nucleus cuneatus of the medulla oblongata) is in this way formed, whilst 
others furnish an enveloping plexus to the ce.Us of the anterior horn and to those of other 
parts of the grey matter. (5.) The descending main branches of the posterior root-fibres 
have, like many of the ascending branches, only a limited course, during which they give off 
collaterals, by means of which, and also ultimately by directly passing into the grey matter, 
they assist in forming the enveloping plexus around the nerve-cells of the segments of the 
cord immediately below that at which the parent root has entered (compare figs. 16 and 20). 

2. Degenerations in the spinal cord resulting from lesions of parts of 
the brain. — Removal of the cortex of the so-called "motor" region of .the cerebral 
hemisphere is followed by degeneration extending along the pyramidal tract in the 
brain and cord (fig. 24). In the spinal cord this tract has for the most part crossed 
to the opposite side, but in man a portion runs for a time as the direct tract along 



OF THE MONKEY (France). 

A, upper thoracic cord from a monkey in which the left marginal 
gyros haid been removed some months before death. Sclerosis in both 
crossed pyramidal tracts, bnt most on the opposite side. 

B, mid -thoracic coni from a monkey in which the right gyrus fomicatus 
had been destroyed some months before death. Sclerosis in the opposite 
pyramidal tract. 

the anterior median fissure on the same side as the lesion (fig. 
14). Although this direct pyramidal tract is usually considered 
to be confined to the anterior column, it is found in the 
monkey as the result of lesions of the motor regions of the 
cortex that there are a few scattered fibres in the circum- 
ferential part of the antero-lateral column which also under- 
go degeneration (descending cerebral fibres of the antero- 
lateral column, see p. 25). The crossed tract lies in the posterior part of the 
lateral column between the direct (dorso-lateral) cerebellar tract and the posterior 
horn, and in this situation the degeneration can be traced downwards, decreasing 
in amount, and, in the lower parts of the cord, with the disappearance of the 
dorso-lateral cerebellar tract, approaching the surface of the cord near the tip of the 
posterior horn. In the cervical region the crossed pyramidal degeneration may reach 
the surface of the cord in front of, i,e,, ventral to the dorso-lateral cerebellar tract, 
which is partly enclosed by the degenerated fibres ; this, at least, is the case in the 
monkey (fig. 25, A). After a unilateral lesion of the cortex there is also a certain 
amount of degeneration in the lateral tract of the cord on the same side as the lesion. 
This is especially the case when the lesion has involved the marginal convolution 
(fig. 25, A). These are not, as might be supposed, fibres which have passed from 
the pyramid of the medulla oblongata directly to the lateral column of the same 
side of the cord, but they may be traced from the lesion of the cerebral cortex 
across the corpus callosum into the internal capsule of the opposite side, whence 
they run down the crusta and pyramid bundles of the pons and bulb to re-cross at 
the decussation of the pyramids, and thus to reach the pyramidal tract of the 
cord on the same side as the lesion. Although most numerous in the higher 
parts of the nerve-centres, a few of these re-crossed fibres are found to extend right 
along the spinal cord. ^ 

On the other hand, section of the pyramidal tract in the cord of the new-bom animal is 
followed by atrophy of the large cells of the " motor " area of the cortex (v. Monakow). 


DeBtmctiou of the gyros fomicatna of one faemisphere is also followad by degeneration 
extending down the pTiainidal troot, although the (rfrne fainicatna oannab be reckoned in 
with the " motor" region of the cortex cerebri, bnt rather uppears to be connected with the 
ftppreciation of Bensory impressions. Since, however, it is not possible to cnt away the gjne 
fomic&toB without paihin^ aside and thos somewhat injuring the motor cortex, it may 
be alleged that the defeneration in question Is really the result of such iajury to that cortex. 
Nevertheless there is no serious improbability in supposing that afferent as well as efferent 
fibres are oonTeyed aloni; the course of the pyramidal tract. Indeed, so far as experimental 
evidence upon animals is of value in determining the course of afferent impressions along the 
cord, it is rather in favonr of some kinds at least of those impressions pLissing up this part of 
the lateral column. 

Harcbi iind Algieri found extensive degeneration in the tracts of Bnrdach after removal of 
a part of the cortex a little behind the motor zone in the dog. and also after removal of the 
occipital lobe; in the latter case combined with some degeneration in GoU's column. Singer 
and Manzer were unable to conSrm these reanlts. 

8herrin[f(on finds, after remoyal of parts of the cortex cerebri, a few scattered degenerated 
fibres in the anterior and lateral cornua of the spinal cord (and also in the grey matter of the 
poos and in the substantia nigra of the crna cerebri). The same observer has noticed that 
even when the cortical lesion is entirely confined to the so-called "arm-area " of the cortex, a 
certain number of fibres are found to de;:enemte rif;ht down the pyramidal tract of the oppo- 
site side, even aa far as the lumbo-sacrat region. 

3. De^nerations in ilie spiaal cord reBolting feoin leaioiui of the cera- 
bellam. — These have been described b; Marchi, who has fuuad, as above mentioned 

Fig. 26. — SseTioi) or spinil cobd or nua (Lt'MDAE rkoios) eillkd 

(p. 25), that removal of one lateral half of the cerebellum 
in the dog is followed by degeneration extending down the 
circumferentinl part of the an tero- lateral column. The 
degeneration is moat extensive'in the npper regions, and 
gradually leBEeoH in the lower parts of the cord, but can 
be traced almost to it; termination. It also extends 
along some of the fibres of the anterior roots, thus indicating a direct connection 
between these and the cerebellar cortex (fig. 26, a, d). 

4. Degenerationi resulting from leaions of the cord itself.—- a. Sec- 
lion of the spinal cord in any part is followed by certain degenerations above 
and certain below the section. These may be classed aa 1, Short degenera- 
tions which extend only a limited distance above or below the plane of section ; 
and 2, long degenerations which extend an unlimited distance upwards or downwards 
in the cord. Of the short de^nerations, the most marked are in the anterior 
column and the anterior part of the lateral column near the grey matter (antero- 
lateral ground- bundle), where there are seen numerous scattered degenerated fibres 
both ascending and descending ; tbey probably are due to the section of fibres 
which serve to connect cells of one segment of the cord to the grey matter of 
other segments above or below. Of the long degenerations, the " descending " 
ones are those of the pyramidal tracts, crossed and direct ; the descendiug 
cerebellar tract of the antero-Iateral column, and, for a few centimeters, the small 
descending tract (comma tract) of the posterior column ; the "ascending" are in 
the posterior column, where they are the same as would have resulted from section 
of all the posterior roots below the point of section, and in the lateral column in 
the situation of the direct (dorso-Iateral) cerebellar tract and of the antero-Iateral 
ascending tract. The continuation of these towards the brain has already been 
mentioned (p. 25) and will again be referred to in connection with the medulla 
a and pons Varolii. 



If the section of the cord is confined to one lateral half the tracts of degeneration 
are limited to the side of the hemiaection, but a few degenerated fibres are seen in 
the corresponding tracts upon the other side above the hemisection {fig. 27). 


fins I 

Medulla olhngata 

rai 12iH DOSSIL keeve. (KA.S.) 
The heroisedion wu on the left side of the cord and complete. The sect! oD- outline* dravn to one 
■cstevith n camera lucida. The degenerated fibres ihown b]' black dots. Those in the section of the 
lambnr cord sre descending, all the rest are ascending, py., pjrsmiital tract ; d.a.l,, descending antero- 
lateral tract ; d.a.c., dorso- lateral ascending cerebellar tract ; d'.a'.d. (in Fona 111.), degeneration of 
fibres of this tract in the white matter of the <;eTebe11ar worm ; v.a.c, Tcntro-latcral ascending cere- 
bellar tract (Oower'a tract) ; v'.a'.c'. (in Pons II. and III.), degenerated fibres of this tract passing 
dorealtjinto the vaWe of VieosaenB (in Pons HI.) and into f.he white matter of tiie vermis (in Fona 11, );, n. v., n.VI., n.VJI., issning fibres of the 3rd, 5th, flth, aad 7th nerre-rooto ; v.JV., 4th 

Keatlj all the degenaration is on the same side as the lesion. A tew fibres are dagenerated on the 
" "it accidental injiirj of that eide of theeord). 

appoaite side (perhaps from a 


Acoording to L. Auerbach destmction in the cat of a coiiBiderable lengrth of the posterior 
part of one half the spinal cord, including the posterior white colnmn, the posterior horn of 
grey mabter, and the posterior part of the lateral column^ is followed by d^i^nerations (ascend- 
ing) in the dorsal cerebellar tract and antero-lateral remainder of the opposite side, with degene- 
rated fibres in the anterior commissure (besides the well-known ascending degenerations of the 
Mime side). The number of degenerated fibres diminishes gradually as they are traced upwards. 
In the medulla oblongata they are few in number and mostly on the side opposite the lesion, 
dorsal to the oliyary nucleus ; a very few on the same side dorsal to the nucleus lateralis. 
The degeneration following a lesion in the lumbar cord is in the ventro-lateral (antero-lateral) 
tract, and is traceable up to the ventral part of the superior worm of the cerebellum ; the dorso- 
lateral cerebellar tract ends more dorsally, also in the superior worm. Some degenerated fibres 
pass through the corpus dentatum cerebelli into the dorsal jiart of the superior peduncle. 

h, DfgtrvcHon of the grey matter of the itphial cord. — This lesion can be ezperimentaUy 
produced in the rabbit by compression of the aorta, lastiug for about an hour (Ehrlich and 
Brieger). The immediate result of the experiment is to cause necrosis of all the nerve-oells 
in the lumbar region of the spinal cord, without immediately affecting the white matter or 
the nerve-roots, a condition which is followed in the course of a few days by degeneration of 
certain fibres, which may be assumed to be those which emanate from the necrosed ceUs. 
If the animal is kept until this degeneration is well marked and is then killed and the 
cord examined in sections, it is found that in the necrosed region and immediately above 
it there is extensive degeneration in all the white columns of the cord, but least in the pos- 
terior columns and in the posterior parts of the lateral columns, where tiie long tracts of con- 
nection with the brain are situated. In sections taken higher up and well above the region 
of necrosis this diffuse degeneration has disappeared, but there is well-marked degeneration 
along the whole length of the cord in the tract of Goll and in the antero-lateral ascending 
tract. It has been inferred, therefore, by Singer and Munzer that these tracts contain long 
fibres which are derived from the cells of the grey matter (of the lumbar region). 

0, Destruction of the cells of Clarltes column along a certain length of the cord is followed 
by well-marked " ascending " degeneration in the dorso-lateral (direct) cerebellar tract (Mott). 


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HelwegT} Situdien fiber den centralen Verlauf der vasomotorischen Nervenbahnen, Archiv f. 
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D 2 


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Nerve-tracts degenerating secondarily to Usions of the cortex cerebri. Journal of Physiology, 1889 ; 
NoU on bilateral degeneration in the pyramidal tracts resulting from unilateral cortical Usion, British 
Medical Journal, Jan., 1890; FuHher note on degenerations foUoinng Usions of the cortex cerebri, Joum. 
of Physiol., 1890 ; Outlying nerve-cdls in the mammalian spinal cord, Phil. Trans., toI. clxxxi. 

Siemerllnflr, Ue. ein gesetzmdssiges atiatom. Verhalten der Wurteln in d. verschiedenen Hohen d, 
Riickenmarks, Neurol. Centralbl., 1886 (Monograph publ. by Hirschwald, Berlin, 1887). 

Sinffer, J. , Ueber secunddre Degeneration im RHekenmarke des Jfundes, Sitzungsberichte der 
Wiener Akad., Bd. 84, iii. Abth., 1882 ; Ue, d, Vcrdnderungen am RHokenmark nach zeitvfeiter 
Verschliessung der Bauchaorta, Wiener Sitzungib., iii. Abth., 1887. 


Singrer u. Munzer, JBeitr. z. Anatomic d. CentralncrvenayttemSi insbetondere det Jtilckenmarhes, 
"Wiener Denkschr. Ivii., 1891. 

Spitska, S. C, The comparative aiuUomy of the pyramidal tracts Journal of comparatiTe 
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Neurol. Centralbl., 1885. 

Spronck, C., Contrib. d Vitude expirim. des l6sion* de la moeUe 6pinitre ditermirUes par VarUmie 
jMuaagire de eet organe^ Arch, de phys. norm, et pathol., 1888. 

Steinleohner-Oretschisclinlkoif, Alexandra, Ucbe^' den Bau des Ililekenmarks bei Mikro- 
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Striiinpelly Beitr. z, Pathoio(/ie des Riickenniarkes, Arch. f. Psychiatrie, x. and xii. 

Tak&C8, A., Ueber den Veriauf der hinteren Wurzelfasern im Jiuckaimark utid den Aufbcm 
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Lectures on Degenerations of the spinal cord, 1889. 

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V^aa, P., Ein Beitrag z. Anat. u. Phynol. der Spinalganglien, MUnchen, 1883. 

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Vlpchow, H., Ueber Zelleu in der Substantia yelatiiu>sa Ralandi^ Neurol. Centralbl., 1887; 
Ueber €las Jiilckenmark der Anthropoiden, Anatom Anzeiger, iii., 1888. 

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The brain or encephalon comprises the medulla oblongata and pons Varolii, the 
cerebellum, the mid-brain, and the cerebrum. The medulla oblongata (fig. 28, d) i& 
the part continuous with the spinal cord ; it is the lowest part of the encephalon, 
and rests against the basilar process of the occipital bone. The pons Varolii (c) is 
a direct continuation upwards and forwards of the medulla oblongata, but the name 
also includes the transversely coursing fibres of the middle cerebellar peduncle. The 
cerebellum (b) occupies the posterior fossa of the cranium. Its central part forms the 
dorsal boundary of a space, which is bounded ventrally by the dorsal surface of the 
medulla oblongata and pons Varolii, and which is named the fourth ventricle of the 

Pig. 28. — Plan in outline or thi sn- 

SIDE. \ 

The parts are represented as separated 
from one another somewhat more than 
natural so as to show their connections. 
A, cerebrum ; e, fissure of Sylvius ; B, 
cerebeUum ; C, pons Varolii ; D, medulla 
oblongata ; a, peduncles of the cerebrum ; 
6, e, d, superior, middle, and inferior 
X)eduncle8 of the cerebeUum ; the parts 
marked a, b, form the isthmus ence- 

brain. The cerebellum is con- 
nected by peduncles below with 
the medulla oblongata, above with 
the cerebrum, and in the middle 
with the pons Varolii (c). The 
mid-brain is continued from the 
pons Varolii and comprises the two crura of the cerebrum (a), which are surmounted 
in man and mammals by two pairs of tubercles named the corpora quadrigeinina (b), 
but in oviparous vertebrates by one pair only, then named the corpora bigemina or optic 
lobes. The cerebrum (a) includes all the remaining and by far the largest part of 
the encephalon. It is united with the parts below by the mid-brain, which forms a 
comparatively narrow and constricted portion or isthmus. The cerebrum is mainly 
composed of the large convoluted cerebral hemispheres^ and within it are the third 
and two lateral ventricles. It occupies the vault of the cranium, the anterior and 
middle cranial fossae, and the superior fosssB of the occipital bone. The cerebral 
hemispheres are united together by a large commissure termed the corpus callosum, 
and by smaller commissures (anterior, middle, and posterior). 



The mediilla oblongata or spinal bnlb (bulbus r/uichiticus, Meckel) is continuous 
below with the spinal cord, on a level with the lower margin of the foramen magnum. 
Its upper limit is marked off on the ventral aspect from the pons Varolii, into which it 
is continued above, by the lower margin of the mass of transverse fibres which unite 
the two hemispheres of the cerebellum ; its ventral surface rests in the basilar groove 


of the occipital bone, its dorsal or posterior sarface is directly continaed into that 
of the pons, aod lies ia the fossa named the vallecnla between the hemiBpheres of 

uarcu and fratu nature). (Allen Thomson.) ) 

], 2, 3, 3a, 8ft, are piMed on convolutions of the cerebrum ; 4, the fifth ventiicle, and above it the 
divided corpiw callosnm ; 5, the third ventricle ; 5', pituitary holly ; 6, corpora quart riaemina and pineal 
gland ; + , the fourth ventricle ; 7, pons Varolii ; 8, medulla oblongata ; 9, eerebelluni : i, the olfactory 
liolb i II, the right optic nerve ; iii, right third nerve. 

the cerebellum. From its front and sides the sixtli to the twelftli craninl nerves issue, 
while the fifth nerve emei^ea from between the commissural fibres of the poM. 

The term mednlls oblone-ata. an employed by Willia and TieuwenB. and by those who 
directly followed thpm, included the cmra corebri and pona Varolii, as well ae that part to 
which by Haller first, and by most subsequent wtitera. thin term has been restricted, 


a, a, pyramids ; i, their decunaation ; c, c, olives ; d, (/, 
restiform bodies ; e, external arci/cirni fihrea, curving round the 
lower end ot the olive ; /, fibres described by Sully as pasBiiiy 
from the anterior column o£ the cord to the cerehellum ; g, 
anterior column of the spinal cord ; A, lateral column ; y. 
pons VaroUi ; i, its upper fibres : v, v, roots of the filth pair "i 

The combined mass of tlie medulla oblongata 
and pons has an oblong or rbomboidal form, beiiij.'- 
expanded in the middle, where it is coniinnous 
with the crura cerebelli, and tapering towards the 
spinal cord below aud the mid-brain above. The 
transYcrBely coursing fibres of the cerebellum pro- 
dace a considerable prominence {tuber annulare) on 
the ventral surface of the upper or pontine part of the 
mass ; these fibres are arched upwards so as largely 

to conceal the crura cerebri from the ventral aspect. The length of the medulla 
oblongata from the lower part of the decussation of the pyramids to the pons is 


nearly an inch (20 to 24 mm.), its greater breadth is about three-fourths of an inch 
(17. to 18nim.)i itB thickneaa, from before backwards, is rather lees (15 mm.)- In 
the lower part where it joins the spinal cord, its diameters differ but little from those 
of the cord. The pons Varolii is about an inch long and rather more than an inch 
broad ; it is considerablj thicker than the medulla oblongata. 

The anlmor and posterior median fissures which partly divide the spinal cord 
are continued into similar fissui-es in the medulla oblongata. The anterior fissure 
terminates immediately below the pons in a recess, the foramen cacum of Vicq 
d'Azyr ; it is partly interrupted below by the decussating bundles of the pyramids ; 
the posterior fissure is continued upwards to about the middle of the bulb, it ceases 
at the lower end of the fourth ventricle. 

The strncttire of the medulla oblougata and pons will be most easily made clear 
by tracing the several parts of the spinal cord upwards. 

In doing this it will be found that the relative position and extent of many of 
the parts are gradually alteTed, and that other parts which are not, so far as is known, 
represented in the spinal cord, become interpolated between those which are there 
met with. It will further be found that the change of relative position of the parts 
is largely owing to two causes. In the first place the sudden passage of large 
bundles of medullated fibres from the posterior pait of the lateral column of the cord 
to the opposite side of the anterior median fissure appears to break up to a great extent 
the grcymatterofthe anterior horn, which is traversed by the bundles. In the second 
place the opening up of the central canal and separation of the lips of the posterior 
median fissure bring the grey matter to the surface in the fourth ventricle, whilst Ihe 
posterior horn is coiucidently shifted to the side, much in the same way as it would 
he if a median incision were made from the posterior surface of the spinal cord into 
the central canal, and the two lateral halves were then turned outwards so that the 
sides of the posterior median fissure became the posterior surface of the cord. 

The lines along which the cranial nerve-roots issue from the sides of the bulb 
murk the surface of the latter off into three chief columns on cither side, which may 


WITH TBB HKDULLA OBkoHOATA. (After LocUiart Clarke.) 
/, anterior; fp, posterior fiarara ; p, end of decuasationof pjrxmidH; 
C'la, C'lp, anterior and posterior roots of lint cervioil nerve ; SI, root 
of Bpitial aucesBorj nerre ; e, CKntral canal. 

be termed dorsal, lateral, and ventral respectively. Thus 
the spinal accessory or eleventh cranial nerve (figs. 32, 34, 
35, XT) begins to take origin as far down as the lower 
end of the cervical region of the cord where its roots issue 
from the side of the cord, and lateral to the posterior roots of the cervical nerves 
(fig. :)I). At the upperend of the cervical region, however, they are approached by 
the line of the posterior roots, and some of their bundles arise in conjunction with 
the posterior roots of the first and sometimes of the second cervical nerve. They are 
succeeded by the bundles of the vagus root, and these again by those of the glosso- 
pharyngeal. At the junction of the pons with the medulla oblongata the seventh 
nerve also is seen issuing along the same line, and still higher the large root of the 
fifth is given off from the lateral aspect of the pons. The line of eiit of this 
series of nerve-roots is marked below by a shallow sulcus, but if traced upwards 
it will be seen that the sulcus is obliterated or nearly so before long, so that 
the issuing series of nerve-roots alone serves to mark its position. As it passes 
upwards it becomes gradually diverted outwards ; so tliat opposite the place where 
the central canal opens into the calamus scriptorius of the fourth ventricle, the line 
iu question has left the posterior surface and in the rest of its course runs along 


the lateral surface of the bulb. Towards the upper end it passes near the pos- 
terior margin of an oval prominence on the aur&ce of the bulh termed the 
ohvary body or lower olive {o), but is separated from that prominence bj a tract 
of longitudinal fibres. In transverse sections of the lower part of the medulla 
Fig. 32.— View tnou BKyuRK o; thi 


On the right side the coHTolutiona of 
the central lobe or ialuid of Reil haTe 
been lett, together with a BmsU jiarl of 
the sDteiioT cerebral conroluljoiis : on 
the lett side these have been removed bj 
an incisioD carried between the tlialsmua 
opticne and the cerebral hemiepbere. 

1', the olfactory tract cut short and 
Jying in ita groote ; U, t)ie left oplic 
nerve in tnot of tbe rommiuure ; II', 
the right opUc tract ; Th, the cat Burface 
of the left thHUnniK opticas ; C, the 
central lobe or island of Reil ; Sy, fissure 
of Sjlviua ; X x . anterior perforated 
space ; t, tlieeiternai, and i, tlie internal 
corpus genicalatam ; k, the hypogihysiii 
cerebri or pituitary body ; (c, tuber 
cinerenm with the infundibulum ; n, 
one of the corpora albicantia; P, the 
cerebral peduncle or crus ; III, close to 
the left oculo-niotor nerve ; x , the 
posterior perforated space. 

The following letteraand numbers refer 
to parts in connection with the medulla 
oblongata and pons. PV, pons Varolii : 
V, the greater not of the fifth nerre; +, 
the lesser or motor root ; fl. the sixth 
nerve ; YJI, the facial ; VIII, the audi- 
tory nerve ; IX. the glossopharyngeal ; 
X, the r-neuniogastric nerve ; XI, the 
spinal ».cei!sory nerve ; XII, the hj[io- 
glossal nerve ; C I, the suboccipital or 
tirab cervical nerve ; p a, pyramid ; o, 
olive ; d, anterior median foaiire of the 
■pinal cord, above which tbe decussation 
oE the pyramids ia represented ; c a, 
anterior column of cord ; r, lateral tract 
of balb continuous with e I, the lateral 
column of Uie spinal con). 

oblongata (fig. 33) it is seen that the bundles of fibres of tliese uerve-roota traverse 
the substance of the bulb to reach a group of nerve-cells in the grey matter neai' 
the central canal and thus mark off a somewhat oval area on each side at the pos- 
terior part of the section. This area is termed by Flechsig the posterior area of the 
medulla oblonffala, and the tracts of white fibres which can be traced, as will be 
immediately noticed, upon the surface of this part, may therefore be conveniently 
termed its posterior columns. They correspond in position to the posterior columns 
of the spinal cord. 

The line of origin of the anterior roots of the spinal nerves, allhongh not marked 
in the spinal cord by a distinct furrow like that whence the posterior roots issue, yet 
when traced upwards into the bulb, deepens into a well-marked longitudinal groove 
which is continued almost vertically ss far as the lower border of the projecting 
mass of the pons. In its upper part this groove separates the olivary pro- 
minence from the prominence of the pyramid. Just below the olive it is often 
obliterated for a certain part of its course by a band of transverse fibres. The root- 
bnndles of the hypoglossal nerve (figs. 32, 33, 34, XII) pass out froni'this furtow, 


and thoBC of the sixth nerve emerge in the same line with it hut at the lower border 
of the pons Varolii. In tranBverEe EectionB of the medulla oblon^^ta and pons these 
root-bnndleB may be traced back through the substance of the organ to a gronp or 
column of nerve-cells situated in a portion of grey matter close to the antero-lateral 
side of the central canal in the lower closed part of the bulb (fig. 43), and close to 
the middle of the fourth Tentricle in the upper opened-out part (tigs, 44, 4^)). This 


DCRiPtoRius. (Lockhart CUrke.) 
e, central canal ; /, anterior iiie<1ian fissure ; f.g, funiculus )ira 
IM., tobtrcle of Rnlwido ; o, olivarir bodj ; a.p., pjrsmid ; XI, XII, t 
nerves ; Xf, XII', their nuclei. 


Tbe corpus striatum andthatamaq opticus hare lieen prcservefl in connection with the centrHl lobaand 
cran cerebri, while the remainder of the cerebrum hns bees removed. 

St, upper surface of the corpus striatum ; Th, back part of the thalBmus opticus (iiulTinat) ; C. 
placed on the middle of the fire or sii convolutions constituting the central lobe or island of Reil, the 
cerebral substance being removed from its circumference ; Sy, fiseure of Sylvius, from which these 
convolutions radiate, and in which are seen the white strite of the olfactory tract ; I. the olfactory tract 
divided and hanging down from the groove in the convolution which lodges it ; II, optic nerves a little 
wa; in front of the commiaaure ; a, right corpus albicans with the tuber cinereum and infundibalnm in 
front of it 1 h, hypophysis or pituilajy body ; r, eiternal, and i, internal corpus geniciilatuui at the 
back part of the optic tract ; P, peduncle or orus of the cerebnim ; III, right oculo-motor nerve; p, 
pineal gland ; g, corpora quadrigemina ; IV, trochlear nerve rising from v, the valve of Vieuasens. 

The following numbers and letlere refer chiefly to parts in connection with the medulla oblongata and 
pons. V, placed on the ))onB Varolii above the right nerviis trigeminus ; n, thesunerior, m. the middle, and 
in, the inferior peduncle of the cerebellum cut short ; VI, the sixth neive ; VII, facial nerve ; VIII, 
auditory nerve ; IX. the glosso- pharyngeal nerve : X, placed opposite to the cut end of the pneomo- 
gastric nerve ; and XI, the uppermost fibres of the spinal accessory nerve ; XII, the hypoglossal nerve ; 
p a, pyramid ; o, olive ; a r, arciform fibres ; r, restiform body ; Ir, tubercle of Rolando ; c a, ant«rior, 
D p. posterior, and c I, lateral columns of the spinal cord ; C I, i, anterior and posterior roots of the 
ittt eerrlcal utrre. 


portion of grey matter is contittnona below with part of the anterior horn, and the 
roots of the hjpt^loasal and sixth nerve appear to correspond generally with the anterior 
roote of the spinal nerves. In traveling the substance of the bulb they mark off an 
anterior arm, wedge-shaped in transverse section, which is placed between them and 
the anterior median fissure. This area is on the surface marked by the prominence 
known as thB pi/ramid or anli-rior pyramid, which corresponds in position (but only 
to a email extent in the fibres of which it is composed) with the anterior coliunn of 
the spinal cord. The remainder of the transverse section of the bolb, after the 
posterior and anterior areas are deducted, lies between the line of nerve-root bundles 
of the hypoglossus and aiith ou the one side, and that of the successive bundles of the 
spinal accessor}', vagus, glosso-pbaryngeal, and seventh on the other. This is termed 
by Flecbsig the lalfral area, and on the surface it is marked by a continuation 
of part of the lateral column of the cord, and by the prominence of the lower olive 
already alluded to. 

We may now proceed to describe in detail the several parts which appear upon 
the sorfiice of the bulb in the three regions thus marked off by the two seta of 
nerve-roots, commencing with the posterior area. 

PoBt«Tior area. It will he remembered that in the upper region of the 
spinal cord a small portion of the whole posterior column is marked off from tbe rest 
by a well-developed pia-matral septum, and is indicated on the surface by a distinct 


Tbe cerEbFllum nnJ inferior medulUr; vuIdqi, 
and the right half at the superior nwdullary 
rslum, haTB been cut awaj, bo an to eipoae the 
fourth VGDtride. 

p-n,, lina of the posterior roots of thespijiat 
oerres ; p.m.f., posterior median liasure ; 
f.g., lonicolus gracilis; cL, its tlava ; /.e., 
fanicnlna cuneatus ; f-B., fuDicnlus of 

Robodo ; r.b., reatiform body; c.»., lower end ".? 

of the fourth Tentricle (calRmua scriptorius) ; ', 
■ection of the lingula or tienia : pnrt of the "o' 

choroid ple),iiB is seen beneath it ; Lr., lateral tjoJf 

reeesB of the ventricle ; ttr, sCriic acusCicie ; i.f., 
inferior (poaterior) fovea ; s/., Baperior(anteriDr) f^^ 
forea; between it and the median sulcus is the 
fumculns terea ; eU, cut sui-face of the left 
cerebellar hemisphere ; n.d., central gre; matter / 
(nocleoa dentatns) seen as a wavy line ; Lm.r., 
superior (anterior) medulla:? velam ; Ing, lin- 
gnia; i.c.p., superior cerebellar peduncle cut 
loDgitudiiuUiT ; ct, combined section of the 
three cerebellar peduncles (the limita of each are 
not marked) ; c.q.i., cq.i., corpora qusdrigeniin a 
(miperiar and inferior) ; fr, fnenulum veil : /, 
fibres of the fillet, seen on the surface of the teg- 
mentum ; c, cruala : l.n., lateral grooTs ; c g.i., 
corpus geniculatum internum ; lA, posterior put 
of thalttmuB ; p, pineal bodj. The Roman num- 
bers indicate the corresiiouding cranial nervea. 

longitudinal prominence bounded later- 
ally by a shallow groove. The portion 
UiuB marked off is the postero-mesial 

column (tract of Goll), and the prominence, which is continued up into the medulla 
oblongata, becomes there still bett«r marked, and is known as the funiculus gracilis 
(fig. 85, /.g). This, as it is traced upwards, especially as the fourth ventricle is 
approached, broadens out into an expansion termed the clava (cl), and as the ventricle 
opens out the clavee of opposite sides diverge and form the lateral boundary to the 


ventricle in its lower pHrt. Above, the clavte are tapered off and soon become no 

longer traceable. 

The fonicnli (tmciles with their clavfeare soraetiines described as the potteriiv pyramid*. 

Between the postero-meaial column and the postero-lateral groove from irhioh 
the posterior roots of the cervical nerves pass out there is found ia the npper part of 
the coi-d a single distinct column, viz., the postero-lateral column {tract of Bardach). 
This is also prolonged into the medulla, and also like the funiculus gracilis expands 
as it is traced upwards : it, is here known as the funicidiis cuneatus. Outside this 
fnnicnlas cnneatus and between it and the line of roots of the spinal accessor; 
another longitudinal prominence is caused by the fact that the substantia gelatinoea 
of Rolando begins near the lower end of the bnlb to project towards the surface 
as a distinct funiculus, narrow below but broadening as it is traced upwards, where it 
forms a considerable eminence known as the tubercle of Rolando. The longitudinal 
prominence which passes up into it, is termed therefore by Schwaibe, the fimiculut 
ofRoJandu {fig. 35,/.^.). 

The faniculQB of Kol&tido is termed b; lletile the lateral caceate fuaicnlus. 

On a level with the adjoining' clava of the funioulua (gracilis, the enlar);ed port of the 
caneate faniculua also, like that, ezhibit« a slight eminence, which is best marked in children, 
and has been termed the csncalc Uibrrclc (Schwalbe). 

In the upper part of the medulla oblongata, the cuneate funicnlus is concealed by 
a set of fibres {txtemal arched or arcuate fibres) which issue from the anterior median 

Fig. 36.— DlflSEOTIUN OP T 

(Allen TlioniBon.) 

P, pona Varolii 1 p, tho pyi-amids, the upper part of the 
right one hoe been cut Uiwa; ; p', the fibres of the left 
pyramid, as they ascend through the \Kas. eipoeed bj the 
remoral of the luperfiuial trinauerae fibrei ; p" 'a placed on 
some deeper transverse fibres of the pons on the ri^bt side, 
below the divided fibres of the right pjTxmid ; a, left 
anterior column of the cord, its median part passea upwaida 
into the outer part of the pyramid, the remuoder dips 
beneath the pyraniid und olivary body ; o, oliiarj body ; a', 
the cooUnuutioti <>f part of the lateral colamn asceDdioK 
throngh the puns and exposed by the removal of a small 
portion of the deeper transverse fibres ; o", some of the 
name fibres divided by a deeper incision on tlie right side ; 
/, V, the Uteisl ooluDina of the cord ; x . their deeper parts 
passing by dcvussation into the pyiamids ; r, direct cer«- 
bellar tract passing from the lateral column into the inferior 
peduncle of the cerebellum, or restiform body ; r', fawiculos 
passing from the anterior column to the same ; ft, deep 
' lungitudinal fibres derived from the anterior and later^ 

tolumns of the curd, 
r pe li, explanafory outline of the section of the spinal cord. 

It, anterior colunma ; p, posterior ; I, lateral. 

fissure and passing laterally over thesnrface of the pyramid and olive, turn upwards 
to join the restiform body. There is also a narrow strand of fibres from the lateral 
colamn of the cord, marked by its white appearance, which joins this tract of oblique 
fibres just above the level of the tubercle of Rolando. This is the dorso-lalerat (direct) 
cerebellar tract which has been already noticed in the description of the spinal cord. 
These obliquely crossing fibres turn upwards as they cross the funiculus of Rolando, 
and appear to blend with that column and with the cuneate funiculus. They do 
not, however, actually blend with thera, but are reinforced by a large number of fibres 
coming from the opposite side of the bulb {see p. 52, fig, ii), and the whole mass 
of fibres thus produced forms a rounded, prominent cord, the corpus resttforme, or 
-like body (fig. 86, r), which passes directly into the corresponding hemisphere 
of the cerebellum, constituting its inferior peduncle. 


L»t««l »r«a. — The lateral column of the spinal cord appears, on the surface, to 
be directly continued upwards into the lateral area of the medulla oblongata. In 
reality, however, a considerable tract of the white fibres — that which in the spinaj 
cord we have noticed as the lateral pyramidal tract — is found, at the upper end of 
the spinal cord, to cross obliquely in stout bundles through the grey matter of 
the anterior horn, and across the anterior median fissure to the other side of the bulb, 
where it forms the mesial and larger part of the pyramid (figs, 36, ^7). The rest of 
the late rail col umu can be traced vertically upwards (with the exception of the dorso- 
lateral cerebellar tract which passes backwards into the restiform body) as far as the 
lower end of the olive whei-e its longitudinally coursing fibres become concealed by 
this prominence and by the arched fibres already noticed. 

The olivary body or lower olive (figs. 82, Si, 36, o) is, as its name implies, an 
olive-shaped prominence, which lies in the upper part of the bulb, immediately above 
the apparent termination of the lateral column, and extending nearly as far as the 
lower border of the pons, being only separated from this by a deep groove in which 
is sometimes a small band of arched fibres. The line of exit of the hypoglossal 
nerve-roots lies on its inner or mesial border, that of the accessory, vagus and glosEo- 
pharyngeal roots along its outer side, hut the latter are separated from it by a groove 
in which longitudinal fibres prolonged from the ventro-latera! cerebellar tract can be 
seen. Sometimes there is a smalt longitudinal tract running along its inner border 
also, and in such case, with the arched fibres above and below, the olive appears to 
he entirely enclosed hy a fibrous strand, which has sometimes been descrit>ed as it« 
capsule (Hligva oliva). This name is, however, more applicable to a layer of fibres 
which immediately surrounds the dentate nucleus of the olive (see note on p. 56, 
and fig. 44, i.o.). The longitudinal tracts on either side of the olive are often con- 
cealed iu great measure by the arched fibres, which may form a complete superficial 
layer over the olive, and indeed over the whole anterior and lateral surface of this 
upper part of the medulla oblongata. 

Anterior afea.— The anterior columns of the cord, although on superficial 
inspectioa they appear to be prolonged into the pyramids of the bulb, are so 

Fig. 37.— SioTioK or thb munLLA OBLimaiTA at thk hiddli u? ,■, f.g 

TBI DtOUSSlTTUR Of ia% PIBAHlIXt. (L»cU»rt Cluks.) '' | 

/, ■ntcrior; /.p., poBbirior fioure ; a.p., pyramid ; a, remains 
of part of anterior coma, Beparatei! b; the crossiag bandlei from 
the rest of the grej matter ; I, contiauation of lateral cotumD of 
cord ; R, coDtinuatioa of aabstantia gelatinoea of Rolaada ; p.c, 
continoa^on of pnaterior comu of grej matter; f.g., fnniculua 

only to a small extent. For the lateral pyramidal 

bundles, crossing the anterior median fissure from the 

lateral column, are continued upwards close to that 

fissure, and unite with the comparatively small anterior 

pyramidal bundle to constitute the prominence known «-' 

as the pyramid (anterior pyramid). The prolongation 

upwards of the rest of the anterior column of the cord lies deeply, being altt^ether 

concealed from view by the pyramids. 

The' pTTUaids (figs. SO, a, 32, pa), are more prominent above than below. 
They are bounded mesially hy the anterior median fissure, and laterally by the 
olivary bodies, being separated from these by the groove before mentioned, ftom. 
which the roots of the hypoglossal nerve issue. At their upper end they are 
constricted, and become more completely separated from the rest of the medulla 
oblongata. They are here very frequently crossed by a band of arched fibres, the 


pontkulm of Arnold. Each pyramid then enters the Bubetanca of the pons in one 
lai^ bundle, which soon breaks up into several bundles, and these may be traced 
through the pons into the corresponding peduncle of the cerebrum. 

The decmsalion of the pyramids is the name given to the obliquely crossing 
bundles of the lateral pyramidal tract which are seen in the anterior median fiaaure 
at the lower part of the medulla oblongata. The extent to which the decussation is 
visible varies considerably in different individuals ; for in some the bundles take a 
deeper, in others a more superficial course. Further, in some cases a latter share 
than usual of the longitudinal fibres of the pyramids passes down in the anterior 
pyramidal tract and a correspondingly smaller share in the lateral pyramidal tract. 
And since the anterior tract, which in the pyramid is external to the lateral tract, 
does not cross in the medulla oblongata but merely passes obliquely at its lower end 
to attain the side of the anterior median fissure, the decussation in these cases is of 
less extent. On the other hand, in rare cases, the whole of the fibres of the pyramid 
may cross over at the lower part of the bulb and become lateral pyramidal tract, 
in which case the anterior or uncrossed tract is wanting in the cord, and the 
bulbar decussation is very well marked. All transitions are found between these 
two conditions (see p. 2-1- ). 

The potM Tarolii forms a prominence marked by transverse fibres above and in 
Dxint of the medulla oblongata, and between the lateral hemispheres of the 



Pig, 38.— T«iK3VBRSK aiamoM ihroeoh lokbe piw of puns Viholii. (After StilliDg »nd .Schwalbe.) 
The dewripCion of this figare is given on p. 61. 

cerebellum (fig, ;t8) ; at the sides its transverse fibres are gathered together into 
a compact mass, which passes into the cerebellum, and is named the middle crus 
or middle peduncle of the. cerebellum. On its ventral surface the pons has a shallow 
median groove along which the basilar artery runs, and it ia perforated by small 
branches of the arteiy. The groove is in some meaanre due to the circumstance 
that the pyramids of the medulla oblongata are continued np through the pons with 
a slightly divergent coarse, and thus produce a prominence on either side of the 
middle line, covered, however, by the superficial transverse fibres. 


The pons consists ventrally of transverse cerebellar fibres, between which 
the longitudinal fibres prolonged upwards ^m the medulla oblongata pass ; 
together with a large intermixture of grey matter. The superficial fibres on the 
ventral surface (fig. 30, p) are transverse in their general direction, but while the 
middle fibres are exactly transverse, the lower set ascend slightly, and the superior 
fibres (fig. 30, $), which are the most curved, descend obliquely to reach the eras 
cerebelli on each side ; some of the upper fibres cross obliquely the middle and 
lower ones, so as to conceal them at the sides. When the superficial transverse 
fibres are removed, the prolonged fibres of the pyramids come into view (fig. 36) ; 
these, as they ascend through the pons, are separated into smaller . bundles, 
intersected by other transverse white fibres, which, with those upon the surface, 
are all continued into the middle peduncle of the cerebellum. 

At the lower part of the pons, dorsal to the fibres from the pyramids, is a 
special set of transverse fibres (fig. 38, i)^ named the trapezium (corpus irapez- 
aides) — so called because in most mammals, in which the inferiorly situated fibres of 
the pons are less developed and the pyramids are small, these transverse fibres 
partially appear on the surface in an area of a somewhat four-sided shape. Laterally 
they curve round a collection of grey matter, called the superior olivary nucleus 
(fig. 38, o,s.)y and probably many of them are connected with its cells. They then 
course lateralwards, across the bundles of the facial nerve-roots (F//), and ventral 
to the upward prolongation of the substantia gelatinosa of the tubercle of Rolando 
and the bundles of fibres belonging to the ascending root of the fifth nerve (a.F), 
and appear to become connected with the accessory auditory nucleus (p. 55) and 
with the ventral root of the auditory nerve, of which, according to Flechsig, the 
trapezium forms a cerebral commissure. 

The fourth ventricle. — The external characters of the medulla oblongata and 
pons may be completed by a description of those parts which enter into the 
boundaries of the fourth ventricle. This is the space into which the central canal 
of the cord, after becoming somewhat enlarged and cleft-like, opens out. superiorly 
(fig. 39). The opening-out seems as if effected by the divergence of the funiculi 
graciles et cuneati on either side at an acute angle. These funiculi, which form the 
lateral boundaries of the lower part of the ventricle, bend round laterally at about 
the middle (in length) of the medulla oblongata, so that the ventricle, which is at 
first narrow, rapidly broadens. Opposite the middle peduncle of the cerebellum it 
has attained its greatest width. From this point its upper part again narrows, con- 
verging gradually above to be continued into the comparatively narrow Sylvian 
aqueduct. The ventricle is therefore irregularly lozenge- or diamond-shaped, and 
is sometimes named fossa rhomboidalis. The pointed lower end of the ventricle 
has the shape of a writing pen, and is termed the calamus scriptorius (fig. 39, c.5.). 
At its widest part the fourth ventricle is continued for a short distance on either 
side between the cerebellum and bulb where these come in contact, in the form 
of the pointed lateral recess (l,r,). The lateral boundaries of the ventricle 
are, in its lower or medullary part, the clav8B of the funiculi graciles, the funiculi 
cuneati, and the restiform bodies ; in its upper half the superior peduncles of the 
cerebellum (fig. 39, s.cp,). These pass gradually to the roof of the ventricle as 
they extend upwards. They are at first separated from one another by a tolerably 
wide interval which, however, gradually narrows near the enS of the ventricle, 
the two crura of opposite sides there approaching one another, and their margins 
coming in contact. Boof of the ventricle. The triangular interval between 
the two crura is bridged over by a lamina of white matter marked across with 
grey streaks. This is the superior medullanj velum or valve of Vieiissens (fig. 
39, s,m.v.), and, with the crura, forms the roof or dorsal boundary of the upper 
part of the fourth ventricle. The white substance of which it is mainly composed 


is marked doreally by three or four flat transverse grey laminae, with intervening 
Bnlci, which together constitute the Ungula (tig. 39, liig). This is continued 
laterally into the grey cortex of the cerebellnm, while the aubjacent white subetiuice 
of the velum is in direct continuity with the central white matter of the cerebellum, 

Fig. 39.— PoStlRIOR AMD LiTKHiL Vliw' Or 

The cerel>e11nm and inferior luedullarj velum, 
and tbe rigfat balE of the euperior meduUsi? 
TcluDi, hare b««n cut awaf, bo aa to expose the 
fourth Tentricle. 

p.n., line of the posterior roots of the spinml 
nerves-, p.m./., posterior median fissure; f.g., 
funiculus gracilis ; ci., its clava ; f.c, funiculus 
/■y cuneatus ; f-S-, funitulus of Holando; r.h., 
restiform body; c.»., lower end of tho fourth 
' ventricle (calamus soripliirius) ; I, section of the 

li)(ula or t»nia ; part of the choroid pleins is 
■"■^^ Been beneath it ; l.r., lateral recess of the 
ventricle : tlr, striie scusticai ; i.f., inferior 
(posterior) fovea ; (./., superior (anterior) 
fovea : between it and tbe median aulcns 
is tbe funiculus teres ; cbl, cut surface of 
the left cerebellar heniiaphere ;, eental 
gre; matter (nucleus ilentatus) seen as a vavj 
line; i.m.r., superior (anteriorl medullarf 
velum ; biff, lingula ; i.e.p., superior cerebellar 
peduncle cut Ion gitudi Hall; ; cr., combined KC- 
tjon of Ihe three cerebellar peduncles (the limita 
of each are not marked) ; r.9,11., r.;.i., corpon 
qnadrigemins (superior aud iuferior) ; fr, frenu- 
lum veli : /, fibres of the fillet, seen on the sur- 
face of the tegmentum ; c, ci'usta ; t.g., lateral 
groove ; e.g.i., corpus geniculatum internum ; th, 
poiterior part of thalamus ; p, pineal bod;. The 
Roman numbers indicate thp cornssponding cia- 

inh) which a pointed tent-shaped pro- 
jection of tbe roof of the ventricle extends ( fig. 50, a, in longitudinal section). 
This projection is bounded below by the inferior medullary velum, which in like 
manner is prolonged from the white substance of the central part of the cere- 
bellum. It is less easily displayed than the superior velum, being concealed by 


M.S., median sulcus ; ttr, i 
tine part of tbe ventricle and 

recess ; i.f., inferior (posteriory lovea ; a.c, aia einerea ; t.a., tngonam aeustici ; 
(./,, superior (anterior) fovea, close to the lateral margin of the superior part of 
the ventricle. 

& part of the cerebellum, nbich is attached to its under or 

posterior surface. It will be further noticed in the description of 

the cerebellum. Below the inferior velum the roof is formed 

by a simple layer of flattened epithelium covered by pi a mater: 

but it is not quite complete, for there ie a hole in it termed 

the foramm of Majendie a little above the place where the central canal opens 

out into the ventricle, and there are two other apertures in the epithelial roof 

in the lateral recesses just meDtioned. At the sides and below, this layer 

of epithelium passes into continuity with tbe epithelium covering the floor, 


bnt it Ib somewhat thickened hy the uddition of white nervous matter before 
reaching the lateral boundaries of the floor. This thickening is left aa a slightly 
prominent and often ragged membrane when the epithelium of the roof of the 

A, from bflliinJ ; IJ, profile view of tbe riglit half, the medulla anil yons being supposed to lie tiana- 
parenL The efferent or motor nuclei nre ehaded witb oblique lines, the afferent or aensor; nuclei with 
dots. In A the cITeraDt or motor nuclei are represBnlcd on the right side only, the afferent or sensory 
an tbe left. Ill, IV, ocalomotor and trochlear nucleus; V.d, descendine root of tbe fifth 
nerre ; V. ,. so-culled sensory nucleus of the fifth ; V.a, assending root «f the fifth ; V.m, motor 
nncleus of fifth nerve ; VI, nucleus of abducens ; VII, nucleus of facial ; n. VII, root of facial curvinf; 
round abducena uucleus ; VIII, inner or dorsa! nucleus of auditory ; VIII', outer or ventral nucleus of 
auditory ; IK, X, rago-glosao pharyngeal nucleus ; ii.o., iiutieut amhiguut, accessory or efferent va?o. 
glosso- pharyngeal nucleus : XI, nucleus of spinal accessory ; XII, nucleus of hypoglossal ; Xll', 
issuing roots of hypoglossal. 

ventricle is torn off with the pia mater. It commences at the apex of the clava, 
and accompauies the lateral boundary for a short distance ; then turns over the 
sarface of tbe restiform body and terminates close to the place whence the roots 
of the v^us and glosso-pharyngeal nerves issue. It is termed the lienia or liguia 
(fig. 44, /), and its upper transverse part forms the lower boundary of the lateral 


recess of the ventricle. Another thickening of the roof is seen at the apex of the 
ventricle covering the point of the calamus scriptorius : this is named the ohex. 

Two longitudinal vascular inflexions of the pia mater, known as the choroid 
plexuses of the 4th ventricle, project from the roof into the cavity, one on either side 
of the middle line, covered everywhere, however, by the epithelium of the roof. 
Oflfsets from these pass also into the lateral recesses, from the apices of which they 
emerge, encircled by a duplicate of the ligula, which was termed by Bochdalek the 
cornucopia. The epitheliEd layer of the roof of the ventricle follows all the convolu- 
tions of the choroid plexuses, but is nowhere pierced by them ; it is generally 
described as the epithelium of the plexuses. 

The floor or ventral boimdflu?y of the 4th ventricle is marked at its widest 
part, t>., at the level of the lateral recesses, by some transverse white lines, which 
cross the grey matter of the floor, and are known as the strick meduUares seu 
acusiicm (figs. 39, 40, 41, str). 

These striad are caused by bundles of white fibres which emerge from the raphe, within 
which thej can be traced to the ventral surface of the bulb, and curve outwards over the 
restiform body, where they are usually described as passing into the lateral root of the 
auditory nerve. It is certain, however, that this is not the destiaation of most of the fibres 
of the medullary strisB, which are distinctly to be traced to the flocculus of the cerebellum 
(fig". 49, p. 69). They vary greatly in development even upon the two sides of the same brain 
(compare especiaUy Bechterew, NeuroL CentralbL, No. 10, 1892). 

One bundle of these striee is sometimes seen, usually on one side only, taking a course 
obliquely upwards and outwards, passing at the lateral boundary of the ventricle into the 
middle cerebellar peduncle {aherrarU bundle of stride mfidullares, Klangstab of Bergmann). 

The floor of the ventricle is bisected by a slight median groove. A little on 
either side of this groove and immediately below the striae medullares, is a small 
triangular depression (inferior fovea, fig. 40, «./.), the apex of which extends only as 
far as the striae, but the base is prolonged into two grooves extending one from 
each angle. The inner of the two grooves passes with a slightly curved course 
towards the point of the calamus scriptorius, and thus cuts off a pointed triangular 
area, which is bounded mesially by the median sulcus, and the base of which is 
turned towards the striae acusticae. This area {irigonum hypoglossi) is slightly 
prominent, and constitutes the lower end of the fasciculus teres ; in it is the 
prolongation of the tract of nerve-cells from which the roots of the hypoglossal 
nerve take origin. The outer of the two grooves passes downwards with a slight 
outward obliquity nearly to the lateral boundary of the ventricle, and marks off 
externally another triangular area {irigonum acuslici, ta.), the base of which is also 
directed upwards, where it can be traced into a prominence (best marked in children) 
over which the striae acusticae course. To this prominence the name tuherculum 
laterale seu acusticum has been applied, since the main part of the auditory nerve 
arises in connection with it and with the triangular lateral area below it. 

Included between the two grooves is a third triangular area {irigonum vagi), the 
apex of which is at the inferior fovea, while its base looks downwards and outwards. 
This area has a distinctly darker colour than the rest of the floor of the ventricle, 
and especially than the trigonum hypoglossi on the inner side, which has a whitish 
grey appearance, and it has accordingly been named the ala cinerea (ax). Towards 
the apex it is somewhat depressed, but below it is elevated into a distinct prominence 
{emineniia cinerea). It contains the nucleus of the vagus, and superiorly, near the 
inferior fovea, of the glosso-pharyngeal nerve. 

Above the striae acusticae the floor of the fourth ventricle is marked in 
the middle of each lateral half by a distinct somewhat angular depression in a line 
with the inferior fovea, from which it is separated by the eminence over which the 
striae acusticse pass. This depression is termed the superior fovea (s,f,). Between 
it and the median sulcus is the prolongation of the ftmiculus teres, which is pro- 


minent (emmmlia terfla) opposite the fovea but becomes gradually less bo above and 
below. Extending from the saperior fovea to the upper end of the ventricle, where 
this' narrows to the Sylvian aqueduct, is a ahallow depi-easiou {locus ctBml&us) diatin- 
gaiahed in the adult by its dark grey or slaty tint, which is due to a subjacent tract of 
pigmented nerve-cella (substantia ferruginea). The trophic fibres in the fifth nerve 
have been supposed to be derived from these cells. 


The interna] structure of the mednlla, like the external form, will be best nnder- 
Btood by tracing its several parts upwards from the spinal cord ; and this can be 

n$. 42.— Seotiom or tsi iisduli.a oblonqata at tbr middle ot 

THE DEOUBBATios 07 THE PTBiMiDs (Lockhart Clarke). _. J^ji f-9 

•/, anterior ; f-p-, posterior Easure ; ap-, pftamid ; a, remains 
of faxt of antenor cornii, aeparated by the croasing bundles fmm 
the rest of the grey matter ; (, continuatiDa of lateral column of 
cord ; R, eoDtlDoation of aubetantia gelatinout of Holimdo ; pc., 
contiaoatioa of pnrterior comn of gray matter ;/.j., funiculua 

most readily done by a comparison of the appear- 
ances of successive transverse sections. 

lower or closed pkrt of the modnlla oblon- 
gata. — The first changes are produced, in its internal 
structure as in its external form, by the passage of the 
fibre-bundles of the lateral pyramidal tract obliquely 

through the grey matter of the anterior horn, and across the anterior median fissure 
to the pyramid of the opposite side (fig. 42). By this abrupt passage of a large 
number of white fibres through it, the anterior born is broken np, and one part, the 
caput cornu («), is entirely separated from the rest of the grey matter j whilst only 
Pig. 43. — Smtio.'* or : 

DECcsaATioB. (Bchvatbe.) ] 

a.m./,, aatcrior median fiuuie ; /.a., superficial 
nrdform hbrea emerging from the fisaare ; py, pyra- 
mid ;, nucleus of the arciform Gbrea ; f.a'., 
deep arciform fibres becoming euperficial ; o., lower 
end of olivary cncleus ; o', accessory olivary nucleus ; 
n.^, nucleuB latemlis ; f.r., formatio reticularis; 
/.ti-^i arciform fibrca proceeding from fonnatio reti- 
calaris ; g, substantia geUtinosa of Rolando ; a. V., 
ascending root of fifth nerve ; n.c, Dacleaa cuncacus ; 
n.c'., eitemal cuneaie tiucleuB;/.c., fanieulus cune- 
atos ; «.g., nucleus gracilia ; f.g., funiculus gracilis ;, posterior median fissure; o.o., central canal 
BurroDiided by grey matter, in which are, n.X/, 
y, and, n.U/., nucleus 

the base of the horn remains, as a small 
portion of grey matter close to the antero- 
lateral aspect of t!ie central canal. ""V' 

Tbe separated portion of the anterior 
horn becomes pushed over to the side by tbe development of the pyramid and the 
interpolation higher up of the olivary body between them, so that it comes to lie 
close to the separated caput cornu posterioris (see below). The greater part of 
the grey substance is broken up into a/ormatio reticularis (fig. 4S,f .r.), i.e. a compara- 


tivdy coaree network of grey matter containing nerve-cells, interBccted by bundles of 
white fibres ; bnt a small part, probably representing the lateral horn of the cord, and 
like that containing numerous nerve-cella many of relatively large size, remains for a 
time in the lateral column, near the surface, and is known as the nitcleua lateralit 
(fig. 43, n.l). 

Meanwhile the posterior horns have become gradnally shifted laterally, simnlta- 
neonaly with an increase in size of the posterior columns of the medulla, so that in 
place of forming an acnte angle with the posterior median fissure, they now lie 
almost at right angles to it (fig. 42). Moreover, the caput cornn enlaces and 

Fig. 44. — Tramsvkrse bection aw thi midu 

oMVABi Boor. (K.A.8.) MianiFiED 5 diamitibs. (Pram a photoenph.) 
p.i.b, posteiioi lODgitudinnt bundle ; v.t, nucleuB of funicnliiB teres ; n.XII, nncleaB hfpoglosd : 
ti.X, DueleuB vagi ; n'X, oncleaa ambiguUB ; a, fuciculua BolitariuB ; n.p, nucleus poBlenor (cUD«stUB) ; 
f.T, formatio rcticiilariB ; (, tenia ; t.R, Bubstantia Bolandi ; a. V, asceniiiug root of 6ftli ; c.r, corpiu 
i-CBtifonne ;, iaternat arcuiM fibreg ; X, issuing root of vagua ; n.l, nucleus lateralis ; »', groltps 
of large cella, perbaps belonging t^i nucleuB latfiralvt ;, antero-laterai aBcending tract ; n.d.Ot 
nucleus deutatns olivB ; acc.o, acceaBory olivary nucleua ; i,o, ailiqua oliva ; A.o, hilum olive ; fi, 
pyramid ; /, lillet ; r, rapbe ;, nucleus of arcuate fibres ; ar.cxt, external arcuate fibres. 

comes close to the iurface, where it presently forms a distinct projection, the funiculus 
of Rolando, which, a little higher up, swells into the tubercle of Rolando (fig. 42, R.'). 
At the same time the cervix cornu diminishes in size and like the anterior comu is 
eventually broken up by the passage of tranaverae and longitudinal bundles of white 
fibres through it, into a reticular formation, which then separates the caput cornu 
poeterioria (fig. 48, g.) from the rest of the grey matter, and joias the reticular- for- 
mation derived from the rest of the grey matter. In the tubercle of Rolando the 
caput comu is close to the surfece, and its grey substance can readily be seen, but 
above the tubercle it lies deeper, being covered by a well-marked bundle of white 
fibres, the so-called oacenduig root of tli« flftli nerve (a. V.). and by the obhqne 
arched fibres which are passing over it to form the restifoim body. 


cells, bat from the oellB of tlie Gasseriau gangflion (HU). and Hecondl^. if the eeasorj root of 
the fifth is cut at its exit from the pons, the fibres of the so-catled ascendiDK' root degrenerate, 
but the cells of the adjacent gelatinons Bnbatanoe remain nnaffected (Becbterew). There may, 
boweret', be a ptayaiological connection established with these cells by means of collateral 
fibres, aa in the case of the fibres of the posterior columns of the cord and the snbslance of 
Rolando of the posterior horn. 

The grey matter of the base of the posterior horn undei^oes a considerable in- 
crease as we trace it upwards in sections. Portions of grey matter are soon found 
to extend from it into the funiculi graciles and cuneati, forming the so-called nuclei 
of those columns (fig. 43, «.(?., n.c.). These nuclei are at first naiTow in trans- 
verse section ; but as the central canal approaches the posterior surface of the 
medulla they appear us comparatively thick maBsea, which produce externally the 


TORics (Lockkart Clark«). 
c, central cnnal; /, anterior median Bsaure ; f.g., 
funiculus gracilit ; f.r,. funiciiiuH cuneatua ; t.K., tuber- 
cle of Rolaudo ; 0, oliiar; body ; a.p., pyramid ; XI. 
XII, spinal aOcesBorjand hypoglossal nerves ; XI'. XII', 
their nuclei. 

eminences of the clava and the cuneate 
tubercle. Out«ide the nucleus of the funi- 
culus cuneatUB an accessory or external nu- 
cleus becomes formed (fig. 43, n.c). From 
this nncleus fibres pass directly into the resti- 
form body. The nerve-cells of the gracile 
nuclens are for the moat part larger than 

those of the cuneate nucleus, but those of the accessory cuneate are larger than 
either (50/< to 8O/1). The accessory cuneate nucleus is supposed to represent a 
continuation of Clarke's colomn of the cord (Blumenau), while in the grey matter 
of the nucleus gracilis and principal nucleus cuneatus most of the ascending fibres 
of the posterior column of the cervical cord become lost. 

From the lower parts of these nuclei fibres are seen to emerge and to sweep forwards 
and inwards in a curved manner {internal arched or arcatf Jihrei) towards the raphe 
or septum which unites the two halves of the medulla oblongata. Having here 
intercrossed with those from the opposite side in a decussation which lies above 
that formed by the fibres of the pyramids {decussation of the fltlet), they form 
a considerable bundle of longitudinally coursing fibres which lies just dorsal to the 
pyramid and is known as the fillet (lemniscus). Its fibres receive their myelin 
much earlier than those of the pyramid. On section of the fillet higher np some of 
its fibres degenerate downwards and the degeneration also affects interna! arched 
fibres connecting them with the opposite nuclei. These therefore have their origin 
from cells higher up in the brain. 

Vpper or' TsntriovlaT part of the mediill» oblongata. — When the silt-like 
upper end of the central canal opens out into the fourth ventricle, the small remaining 
portion of the base of the anterior horn, which in the closed part was ventro-lateral 
to the central canal, comes to the surface at the floor of the ventricle, and as the 
sections are traced upward increases gradually in size, producing the prominence of 
the funiculus teres. In it, both in the lower part of the bulb where the canal is 
still closed and above where it has opened out, a, group of large nerve-celli (tuXII.) 
is seen in all transverse sections. From this group (column) of cells the successive 
bundles of the roots of the hypoglossal or twelfth cranial nerve arisesnd pass obliquely 
through the substance of the bulb to leave it on its anterior aspect. The tract of 
nerve-cells is accordingly known as the liypogloBsal nudoiui. 


At the fourth ventricle the hypoglosaal nucleus lies aahort distance from the surface 
covered by a flattened bundle of longitudinally running white fibres, which gives this 
mesial triausle of the calamus scriptorius (trigonum hyjx^lossi) a white appearance. 
Fig. 46.— Section OP THK MEBULLi OBumoiTl 
BODi. (Schwalbe.) ( 
f.l.a., anterior medisn fissure;, nu- 
eleuH arcifocmiB ; p., pyramid; XIl., bundlii 
of h)T)ogliiaaaI nerve emerging from the BurfBCO ; 
at b, it ia seen coursing between the pjrainid uid 
^ the olivary naoleua, o. ; /.a.e., external aroifonn 

fibres; n.t, nucleus lateralis; a., arciforra fitiro» 
panJDg towarda restiform b^j partly throogh 
the BubdtantJa geltttinosa, (/., partly aaperfioial to 
the aacendidg root of the 5th nerve, a.V. ; X., 
huQille of vagoa root, emerging ; f.r., formatio 
reticularia ; c,r., corpus restifonue, beginning 
to he formed, ctieflj by arciform fibres, aopetB- 
cial and deep; «.c., nudeus cimeatus ; n.ff. , 
nucleus gracilis ; (, att-if hment of the ligola ; 
/.»., funiculus solitariue ; n.X, n.X'., two 
parts of the tagus nucleus ; n.SIL, hypoglossal 
nucleus: n.(., nucleus of the fnniculns terea ;, nucleus amhiguus ; r., raphe ; A., con- 
tinuation of anterior column of cord ; o', o , 
accessory olivary nuclei ; p.0,1-, peduncnlus olivie. 

Nearer to the surlace of the floor and nearer also to the median groove is a small 
group of cells, known sometimes as the nuoleuB of the fUticulufl toraa (fig. 46, 
n.l.). The cells are small and appear to give origin to fibres which belong to the 

vago -glossopharyngeal roots. 


PS/., pyramid ; o., olivary nucleus ; V.a,, ascending root of the fifth nerve ; VJiJ,, root of tb« 
auditory ner^e, formed of two parts, a. and b., which enclose the restiform body, c.r. ; n,VIII.p,, 
principal (doriiU) nucleus of the auditory nerve ; accessory nucleus | g, ganglion cells 
in the root ; n./.t., niicleuB of the funiculus teres ; n.XlL, nucleus of the bypoglossal; r., raphe. 

At the base of the posterior horn in the lower part of the bulb, and near the 
centra canal, a group of cells (tig. 43, ». XL) is seen in section, which if traced up- 
wards is found to be pushed to the side as the central canal opens, so that in the 


floor of the ventricle it lies lateral or dorso-lateral to the hypoglossal nucleus. These 
cells form the upper or bulbar part of the nnclens of the spinal aooessory*^ 
Above the level where the roots of this nerve cease to come off a mass of grey matter 
with numerous cells is seen lying lateral to the hypoglossal nucleus in a situation 
near the floor of the ventricle corresponding to the prominence of the ala cinerea 
(trigonum vagi) which appears on the surface, and it extends upwards as far as the 
fovea inferior. In connection with it there arise successivelv bundles of fibres of the 
roots of the vagus and glosso-pharyngeal nerves (10th and 9th cranial nerves) : 
those of the vagus beginning at the commencement of the ventricle, and arising 
along the length of the ala cinerea ; and those of the glosso-pharyngeal coming for 
the most part from the upper part of the ala cinerea, and from beneath the inferior 
fovea. The grey matter in question forms then the principal nnclens of the 
pnenmogastric and glosso-pharyngeal nerves. 

It has been inferred from the clinical and pathological evidence met with in cases of 
bulbar paralysis that the motor fibres to the palate and vocal cords, which leave the medulla 
oblongata by the spinal accessory roots, have their real origin in the hypoglossal nucleus. On 
the other hand the pars intermedia of the seventh nerte is said to arise from the upper end of 
the glossopharyngeal nucleus (Duval.) 

Close to this nucleus, but placed somewhat more deeply in the grey matter, is a 
round longitudinal bundle of white fibres termed ih& funiculus soUtarius (figs. 44,«., 
46,/«.). This bundle, which is surrounded by gelatinous grey matter with many 
small nerve-cells, occupies the same relation to the ninth and tenth nerves that the 
so-called ascending root of the fifth occupies to the trigeminal. Its fibres appear to 
lose themselves amongst the cells of the enclosing grey matter, and this and the 
bundle gradually disappear when traced towards the spinal cord : traced upwards 
they pass out with the bundles of nerve-roots which go to form the vagus and glosso- 
pharyngeal, especially the latter. Both this bundle and those forming the ascending 
root of the fifth have their myelin sheath developed at an eariy period. As His has 
shown, they grow into the medulla oblongata from the ganglia of the vagus and 
glosso-pharyngeal, in the same way as the posterior roots grow into the medulla 
spinalis from the spinal ganglia. 

Lying in the reticular formation and ventral to the principal mass of grey matter 
which here occupies the floor of the fourth ventricle, is a small detached pear-shaped 
mass of grey matter containing nerve-cells, which is connected by a kind of stalk 
with the rest of the grey matter. This nucleus, which was formerly termed the 
nucleus amhiguus, gives origin to fibres which pass along the stalk obliquely towards 
the floor of the fourth ventricle and then turn outwards and forwards to issue with 
the root-bundles of the tenth nerve from the side of the bulb. It is therefore an 
accessory vagal nnolens and, in its relation to the grey matter and in the size 
and character of its cells it is a counterpart of the nucleus of the seventh nerve, 
which appears in sections somewhat higher up (in the pons). A prolongation of this 
nucleus gives origin higher up to fibres of the glossopharyngeal. 

The issuing bundles of the auditory nerve pass partly dorso-lateral and partly 
ventro-mesial to the restiform body. The dorsal division contains a large number of 
nerve-cells (ganglion radicis cocMearis), which probably give origin to many of 
its fibres. Ventral to the restiform body and between the two roots is another mass of 
ganglion-cells, which has been termed the accessory auditory nucleus (Schwalbe) 
{fig. 47, n,VIII,ac), From these cells fibres are seen both in the upper part of the bulb 
and in the pons passing transversely towards the opposite side ; they belong to the 

^ The balbar or accessory part of the nerve : the spinal part of the nerve takes origin in the ventre- 
lateral group of ceUs of the anterior horn of the spinal oord (cervical region). 


Bystem of the trapezium (p. 47). Higher up this nucleus blends with the ganglion 
of the lateral root, the two together forming a ventval nndeiui [for the auditory 
nerve ffig. 49, VIILv.), 

Towards the upper part of the bulb an extensive tract of grey matter containing 
small scattered nerve-cells becomes developed outside the vago-glossopharyngeal 
nucleus. This tract corresponds to the lateral triangular area (trigonum acustici) 
which is seen on the surface outside the ala cinerea. Into it most of the fibi-es 
of the ventral or vestibular division of the auditory nerve apparently pass ; it is 
termed the ixmer or dorsal auditory nndens (fig. 47, n.VIIl.p). Ventral 
to this nucleus is a collection of grey matter with large nerve-cells, the nucleus of 
Daiters. Its cells appear to be connected with the cerebellum, for, it becomes 
atrophied after removal of the cerebellar hemisphere of the same side in the new- 
born animal.* Associated with this group of cells is a longitudinal bundle of nerve- 
fibres which has been termed by Roller the ascending root of the auditory nerve 
(fig. 49, R,), but the precise connection of these fibres with the [roots of the eighth 
nerve has yet to be established. Most of these collections of cells will be again 
noticed in dealing with the structure of the pons. 

The nerve-cells in the hypoglossal nucleus are largest ; those in the principal 
nucleus of the spinal accessory of moderate size, and those in the vago-glossopharyn- 
geal nucleus are small and fusiform ; those of the principal (dorsal) auditoiy nucleus 
are the smallest. There are a number of small cells in the ventral part of the hypo- 
glossal nucleus (small-celled hypoglossal nucleus of Roller), but they do not give 
origin to any of the fibres of the nerve (Forel). 

Nucleus of the olivaxy body. — Besides those collections of grey matter which 
are traceable from the grey matter of the spinal cord, portions occur in certain parts 
of the medulla oblongata, which are not represented in the cord. Of these the most 
striking is the nucleus of the olivary hody^ which has been termed, from its appear- 
ance in section, the corpus dentalum of the olive {^g, 44). It is enclosed in the 
olivary prominence, and is therefore situated in the lateral area of the bulb, but 
the grey matter is not visible from the surface, being covered by both longitudinal 
and transverse white fibres. It takes the form of a thin wavy lamina, which is 
curved round at its edge so as to form an ovoid scalloped capsule. The open part or 
hilum of this looks towards the middle line and receives a considerable tract of white 
fibres, which emanate from the raphe, being derived to all appearance from the 
opposite olive, and pass into the hilum along its whole extent, forming the so- 
called olivary peduncle (p.o,),^ Under the microscope the nucleus appears as a wavy 
band of neuroglia, with small multipolar nerve-cells embedded in it. The fibres of 
the olivary peduncle diverge as they pass to the grey lamina. They are partly lost 
in the grey matter of the olivary nucleus but mostly pass in small bundles through 
the lamina, those which are more posterior turning backwards and coursing obliquely 
through the posterior part of the lateral area to join the restiform body and thus to 
pass to the cerebellum as internal arched fibres. These internal arched fibres are 
easily distinguishable by their small diameter from the large internal arched fibres 
which belong to the tract of the fillet : moreover they develope their myelin sheath 
later. Others after coursing through the grey lamina and running between the longi- 
tudinal fibres which cover the olive reach the surface, where they bend round and are 
continued as part of the layer of external arched fibres into the restiform body. 
Through the restiform body, the arched fibres and the fibres of the olivary peduncles, 
the cerebellar hemisphere of one side is connected therefore with the olivary nuclei 

^ The nucleus of Deiters was formerly regarded as giving origin to part of the auditory nerve, and 
18 also known as the outer or tuperior auditory nucleut (see p. 62). 

' Some fibres emerge from the hilum and turn sharply round the ventral and lateral borders of the 
dentate nucleus, to which they form a kind of capsule (fig. 44, s.o.). 


of both Bides. Bnt the connection with the opposite side is the more intimate, for 
it is fotmd that in cases of atrophy of the cerebellar hemisphere of one side, the olive 
of the opposite side is atrophied while that of the same side is intact. And it was 
fonnd by Gudden that after removal in the new-bom animal of the one cerebellnr 
hemiephere, the opposite olive was atrophied. On the other hand the olivjary 
nncleua appears to be connected with the cerebral hemisphere of the same side by 
a tract of longitudinal fibres which lies lateral and dorsal to the nndeus in the 
medulla oblongata, and passes up towards the brain in the reticular formation. Thus 

r.O., reticnlarig alba ; T.g., reticuJaria griBea ; between them a root-bundle of the hypogloBsns (Z77), 
The laDgitndiniil Gbreg ot tiie reticular formation are cut across ; the traosTersel; coursing fibrGB are 
internal annate fibres, piusing on the right of tbe ligiire towards the mphe. 

the olives are intermediary stations between the cerebram and cerebellum : they have 
no direct connection with the cord (Flechsig), 

Besides the main olivary nucleus two smaller isolated bands are generally seen 
(figs. 43, 44, 46), looking like separated portions of the chief nucleus. They 
are situated one ou tbe dorsal, and the other on the meriial aspect of the chief 
nucleus, and are known as the outer and inner accestory olivary nuclei. They 
are traversed like the main nucleus by bundles of internal arched fibres going to 
the restiform body, and are frequently connected at one or two places to the main 
nucIeoB. The inner accessory nuclei are sometimes termed the pyramidal nuclei, 
for they lie immediately behind the pyramids. The root-bundles of the hypoglossal 
nerves generally pass between them and the chief olivary nucleus after traversing 
tbe olivary peduncle, bnt sometimes the nerve pierces the chief nucleus near its mesial 

Other small collections of grey matter and nerve-cells are scattered in certain 
parts of the formatio reticularis, as well as one or two distinct tracts in connection 


with the external arched fibres, and a considerable amount in the median septum or 
raphe. These three structures may therefore next be described. 

The formatio reticularis (figs. 43, 44, 46,/.r.) occupies the whole of the anterior 
and lateral areas of the bulb, dorsal to the pyramids and olives respectively. It is 
thus named on account of the appearance which it presents in a transverse section 
viewed under a moderate magnifying power. This reticular appearance is 
caused by the intersection of bundles of fibres belonging to two sets which run at 
right angles to one another. Those of the one set are longitudinal, and these are 
intersected by transverse fibres, which pass obliquely from the raphe outwards and 
somewhat backwards with a curved course towards the funiculus gracilis and funiculus 
cuneatus, and the olivary nucleus ; and also in the upper. part of the medulla oblongata 
towards the restiform body. 

In some parts grey matter with nerve-cells enters into the constitution of the 
formatio reticularis. The cells are especially large and numerous in the reticular 
formation of the lateral area near the anterior area, where in the lower part of 
the medulla oblongata is situated a remnant of the anterior horn ; and its grey 
matter is presumably derived in great measure from the latter. In the anterior or 
mesial area of the bulb, nerve-cells are mostly absent from the formatio reticularis, 
and this is therefore sometimes distinguished as the forTnatio reticularis alba (fig. 48, 
r.a.), from the other or formatio reticularis grisea (r.g,). 

The longitudinal fibres of the reticular formation of the anterior area comprise 
at least two sets, viz. : — (1) those which occupy the tract nearest to the pyramids and 
which belong to the tract of the fillet above described ; and (2) those which are pro- 
longed from the remainder of the anterior column of the spinal cord after the passage 
of the anterior (direct) pyramidal tract into the outer side of the pyramid. The 
latter become in the higher levels of the medulla oblongata gradually obscured or 
replaced by an accumulation of grey matter which resembles that of the grey reticular 
formation and has been termed by Roller, nucleus centralis. But some of the 
longitudinal fibres of the anterior area remain distinct, and become in the upper 
regions of the medulla oblongata collected into a compact bundle which is known 
as the posterior or dorsal longitudinal bundle. 

The fibres of the reticular formation of the lateral area are prolonged from the 
remains of the lateral column after the lateral pyramidal tract and the dorsolateral 
cerebellar tracts have passed to their respective destinations. Those which are 
nearest the olivary nucleus mostly belong to the anterolateral cerebellar tract (fig. 44). 
The fibres of the lateral area are added to as we trace them upwards in sections, the 
increase being due either to the turning upwards of some of the inner arched fibres 
or to the accession of fibres which are derived from nerve-cells in the grey matter 
near the posterior surface, or in the grey reticular formation. 

According to Deiters, the nerve-fibre processes of the nerve-cells of the reticular 
formation all pass downwards, while their branched processes are directed 

The arched or arcuate fibres of the medulla oblongatii, which have been more 
than once alluded to, are the curved fibres which are seen in transverse sections 
coursing in the plane of the section. From their position they are distinguished into 
external and internal, or superficial and deep. 

The outer or superficial arched fibres (figs. 44, 46) emerge for the most part 
from the anterior median fissure, and passing over the pyramids and olives, many 
of them go to the restiform body. They are added to by deep fibres which come to 
the surface partly in the groove between the pyramids and olives, partly after passing 
through the olives, as before mentioned. Traced back in the anterior median fissure 
they are seen to enter the raphe, and to cross over in it \ after which it is supposed 
that they may become longitudinal, but their further course is not certainly known. 


The imter or deep arched fibres emei^ from the raphe, and traverse the thickncM 
of the bulb, tending towarda the olives, the restiform body, and the nnclet of the 
cnneate and slender funiculi. Those which pasa through and in front of the olives 
are in continuitv with the superficial arched fibres. 

Traced backwards into the raphe, the deep arched fibres cross obliquely to the 
other side of the medulla, where some become longitudinal, joining the fibres of the 
fillet. Others are the fine fibres before alluded to as connecting the cerebellar 
hemiEphere with the opposite olive. 

Pig. 49. — TsAioviME BicnoB cr poirs V.iBOLn t . . 

(B.A.S.) (From a pbotogispb. ) MsgniGed about 4 diitmeterB. 
t.IV., 4th ventricle ; c, vhit« matter of ccrobellar bemiaphere ; c.d., corpus dentaCum cerebtlli : 
jt,, flocculug ; c.r., corpiu reatiforme ; S, SuUer'g aacending auditory bundie ; D, Deiter'i nucleus ; 
VIII, iBsaing root of auditory nerre ; VJJLd., dorsal nucleui ; Vlj/.v., ventral (acccsscry) uucleas 
of au'liloty ;, small-celled nucleus traversed by fibres of the trapeiium ; (r., trapeiinm ; /., 
fillet ; p.l.b., poElerior longitudinal bundle ; f.r., formatio reticulario ; n, n', n", nuclei in formstio 
reticularis ; V.a., ascending root of Sth ; s.g,, subatantia gelatinoaa ; >.a., upper olive : F7/. isauing 
root of facial ; n. VII., nucleus of facial ; VI, root bundlea of abducens ; pj/., pyramid bundles ; n.j)., 
nuclei pontia. 

Vnclai of the superficial ardied fibres. — Amongst the superficial arched 
fibres, or between them and the subjacent coluraos of the bulb, small collections 
of grey matter with nerve-cells are here and there met with, which are distinguished 
by the above name. The principal group of cells lies superficial to the pyramid on 
either side (figs. 44, 46, This group becomes very largely developed at the 
jnnction of the medulla oblongata with the pons Varolii. 

The raphe or septum (fig. 44, r) is composed of fibres which run in part dorso- 
ventrally (fibr^ rectse), in part longitudinally, and in part across the septum more 
or leas obliquely. Intermixed with the nerre-fibres are a number of nerve-cells in 
grey matter. The fibree rect^ are continuous ventrally with the superficial arched 
fibres, which emei^ at the anterior median fissure ; dorsally in the upper part of the 
bulb with fibres firom the medullary Btrife (cf. p. 50). The longitudinal are chiefly 


fibres which have passed into the raphe as fibree reotaa or as superficial or deep ardhed 
fibres, and in it have altered their dh'ection and become longitudinal. The obliquely 
crossing fibres are the deep arched fibres which enter or emerge from the raphe. 
Others, however, seem to come from the nuclei of the nerve-roots, and these may 
pass more directly across as commissural fibres either into the reticular formation or 
into the pyramid of the other side, in either case becoming longitudinal. The nerve- 
cells of the raphe are multipolar cells, those in the middle being chiefty spindle- 
shaped. The latter are connected with fibrae rectse (Clarke), whilst the more laterally 
situated ones, at least those near the anterior median fissure, are connected with 
some of the superficial arched fibres. 

Internal stmctnre of the pons Varolii. — Sections of the pons are greatly 
modified by the appearance of the transversely coursing fibres between the two halves 
of the cerebellum which have already been noticed. These occupy the whole of the 
ventral portion and enclose and conceal from view the bundles of the pyramids, which 
can be traced upwards into and through the pons from the medulla oblongata. 

Between the bundles of fibres of this ventral portion of the pons grey matter 
with small multipolar nerve-cells is everywhere found {nudeipontis (fig. 49, n.p.)). 
It is probable that many of the transverse fibres terminate in this grey matter and 
are through it connected in some way with the longitudinal fibres of the pyramidal 
tract ascending through the pons ; but the transverse fibres do not appear to turn 
upwards, for they are smaller than the longitudinal fibres. 

The posterior or dorsal portion of the pons is chiefiy constituted by a continua- 
tion upwards of the reticular formation and of the^ grey matter of the medulla 
oblongata. As in the latter, there exists here also a median septum or raphe, which 
is similar in structure to that of the medulla oblongata. It does not extend through 
the ventral half, being obliterated, or nearly so, by the great development of the 
obliquely and transversely passing fibres, except near the upper and lower borders 
where the superficial transverse fibres of the pons turn in at the middle line ; and 
especially at the upper border where bundles of the same fibres encircle the crura 
cerebri as they emerge from the pons. 

In the reticular formation, in addition to the scattered and reticularly arranged 
grey matter with nerve-cells everywhere met with, there are one or two more 
important collections which lie embedded in this formation and from which nerve- 
fibres arise. One of these is the superior olivary nucleus, another is the nucleus of 
the seventh or facial nerve, and others give origin to portions of the fifth nerve. 

The superior olivary nucleus (fig. 50, o,s.) is a collection of small nerve-cells 
which lies dorsal to the outer part of the trapezium, in what would correspond (as 
indicated by the passage outwards of the roots of the sixth and seventh nerves) to a 
prolongation of the lateral area of the medulla oblongata. In man it is very much 
smaller than the inferior olive, to which it does not present much resemblance in 
form, although in structure and in the size of its cells there is a close similarity. In 
some animals, however, it is larger, and has a distinctly sinuous outline. From it, 
as above mentioned (p. 47), fibres pass into the trapezium ; it may be connected 
through these with the accessory auditory nucleus of the opposite side (p. 55). 
Running upwards on the mesial side of the superior olive between this and the fillet 
is a bundle of fibres which has been termed the central tract of the tegmenhim, but its 
connections have not yet been satisfactorily ascertained. 

Besides its connection with the contra-lateral accessory auditory nucleus through the corpus 
trapezoides, the upper olive is connected, according to Bechterew, (1) to both the posterior 
(inferior) corpora quadrigemina through the lower fillets, (2) to the cerebellum through the 
restiform body, (3) with the nucleus of the sixth nerve (and perhaps, also, with that of the third 
and fourth nerves) through the posterior longitudinal bundle, and (4) with the spinal cord through 
fibres passing down the anterior column. 


The nncl«iu of the &oial narre (n. VII) liee in the reticular fonuation jast 
dorsal to the superior olivary nucleuB, and at some depth, therefore, below the floor 
of the fourth ventricle. It beginB to be visible in sections immediately above the 
medulla oblongata, in the form of small isolated groups of nerve-cells, from which 
separate bundles of fibres proceed, and extends three or four millimeters upwards. lis 
cells are of moderate size, and their axis-cjliuder processes are directed inwards and 
backwards towards the grey matter of the floor of the ventricle, where they collect 

Fig. 50.— Skctiuk icouHs tbi lovm paut uv the I'ukb (after Stilling and Schwalbe). 1 
pyt pynkioid-banclleB i^atinued up from tht medulla ; po^ tramver^ fibres of the pons passing from 
tha'middle cms of the cerebellum, before (pa^) itad behiud i,po') the chief pyramid bundles ; I, deep<ir 
transieiBe fibres, constituting the trapezium ; the gre; matter between the tnuisveree fibres i> not 
represented either in this or in the following figures ; r, raphe ; o.i., superior olirary uocleus ; a. V, 
bundles ot the aucending root of the Gftb nerve, enclosed by a, prolougatian of the grey snbetAnce of 
Rolando ; Vf, the sixth nerve ; n. VI, its nucleue : F//, the facial nerve ; Vlia, ascending portion of 
the facial root ; it. VII, its nucleus ; VJII, superior root of the auditory nerve ; n. VIII, part of the 
uacleus of Deitera ; o, section of a vein. 

to form a longitudinal bundle, oval in section, which rnns for a short distance 
upwards in the grey matter and then tnrns sharply in a ventrolateral direction, 
traversing the thickness of the pons to emerge on its lateral aspect (fig- 41, B.) 
From facts brought forward by Mendel and supported by Tooth and Turner, the 
facial nerves appear to receive some fibres through the posterior longitudinal bundles 
fW)m the oculomotor nuclei ; these fibres probably being those for the frontalis, 
corrugatoraupercilii, and orbicularis palpebrarum. On the other hand the fibres to 
the orbicularis oris may arise from the hypoglosaal nucleus. 

The motor nndoTUi of tli» fifth narrs (fig. 51, nV) comes to view 
in higher sections through the pons, situated a little below the surface close to 
the lateral margin of the fourth ventricle. It contains large pigmented multipolar 
nerve-cells, the axis-cylinders of which pass ont into the motor root of the trigeminal. 
Fibres are also seen in the grey matter of the floor of the ventricle connecting both 
this motor nncleuB (and also the sensory nucleus, immediately to be described) with 
the raphe, and through this probably with higher parts of the brain. 

The BO-called upper senaory nndeiu of the fifth nerve (n. V) lies on the 


outer aide of the motor root. The cells are Btnall and arranged ia cloBtera sepa- 
rated by the fasciculi of origin of the sensory nerve-root. This collection of cells 
IB more extensive than the motor nncleus, being seen in sections Jiigher np tbe 
pons, and passing below into the so-called " lower sensory naclens," which is a 
continuation of the grey matter of the tubercle of Rolando, and ultimately, 
therefore, of the substautia gelatinoea of tbe posterior bom of tbe spinal cord. 
Passing towards this nucleus into tbe issuing roots of tbe fifth nerve is seen, as 
has just been mentioned, in all sections through the middle part of tbe pons 
a well marked tract of fine fibres which are traceable over tbe posterior longi- 
tadinal buadte to tbe raphe, and ultimately pass, it is believed, upwards 
towards the mid-braiu. This tract is known variously as the crossed root, 
the rapke-Tool, or tbe central tract of the trigeminal, Ite fibres pass by and 


Tbe section paaees tbrangh tbe lower part of the 
motor nucleus (ni/) from wb[ch a handle of fibres oE 
the iDotor root, V\ U seen ptuBing ; Apart of the tipper 
eenaoiy nudeus (nv) U nUo ebown in the aeotian in 
the farm of a number of small isolated portions of 
gre; matiar. Amongst thesB are a few bundles of 
tbe ucending root cut acrosa. but most oE these 
have already become diverted ontwarda to join and 
ssaist in forming the issuing part of tbe main or 
sensor; root, V ; ar, arcuate fibres near the fourth 
ventricle, which «ime partlj from the raphe, partly 
fi-om a small longitudinal bundle of fibres \l) near 
the median buIcub (in.a. ), and pom outwards tn join 
the root of the fifth nerre ; /. r. , formatio reticnlaris ; 
T, , raphe ; (./, , substantia ferruginea. 

may in part be continuous with a small oval 

bundle of longitudinal fibres (fig. 51, I), 

which lies in the grey matter not far from 

the median sulcus, and which resembles in 

appearance the ascending part of the facial 


The rest of tbe grey matter of the pons lies near the dorsal surface and appears 

in the floor of tbe upper part of the fourth ventricle. Besides scattered nerve-cells, 

others are collected at certain parts into definite groups or nuclei from which some 

of the remaining cranial nerves take origin. Like the similarly placed nuclei in 

the medulla oblongata, these also do not lie close to the epithelium which covers the 

surface, but are separated from it by a layer of gelatinous sabstance (neuroglia) free 

from nerve-cells, termed the ependyma of the ventricle. 

The donal naclsns of the anditory nerve (fig. 47, n. VIII p.), is prolonged 
upwards underneath tbe strise acnsticse into the pons (fig. 49, Vlll.d.). It is widest 
at about the junction of the medulla and pons, where it extends almost to the middle 
line ; furtberup it rapidly narrows and becomes shifted towards the lateral boundary 
of the ventricle as the nucleus of the sixth nerve makes ita appearance between it 
and the median sulcus. Its cells are small, and it is much broken up by tbe pas- 
sage through it of fine transverse nerve-fibres. 

Tbe so-called outer or superior nucleus of the auditory nerve, or tbe naclens of 
Deitera (Laura) (fig. 49, D ; fig. 50, n. VIII), is characterized by the lai^e size of its 
cells, and lies immediately ventro-lateral to the dorsal nucleus, which has jnst been 
described. It does not begin to be visible so far down as the latter, but is 
continued as far upwards, rather increasing in size superiorly, whereas the dorsal 


nucleus diminishes. Ifc is much broken up by longitudinal fibres (ascending 
auditory fibres of Roller). The connection of this nucleus with the auditory nerve 
is very doubtful. It undergoes no alteration when the auditory nerve is severed in 
the new-bom animal, whereas section of the spinal cord in the upper cervical region 
of the new-born rabbit is followed by degeneration and atrophy of this nucleus 
(Monakow). It becomes atrophied after removal of the cerebellar hemisphere of 
the same side in the new-bom animal (see also p. 55). 

The Tentral nnoleos of the anditory nerve (see p. 55) which is represented 
in the upper part of the medulla oblongata by a collection of nerve-cells lying in the 
angle between the restiform body and the two portions of the root of the auditory 
nerve (fig. 47, w. VIILac) and by cells interpolated amongst the fibres of the cochlear 
root (p. 55), is placed in the region of the pons between the restiform body and the 
floccalas, and the cochlear root here issues directly from it (fig. 49). Its cells, which 
are small and rounded but multipolar, are enclosed like those of a ganglion, each in 
a nucleated capsule. 

The nndens of the sixth nerve (common nucleus of the sixth and seventh 
of some authors) consists of a groap (column) of large multipolar cells lying on 
either side of the median sulcus (fig. 50, n,VI). It corresponds to the part of the 
fasciculus teres which lies immediately above the medullary striae on the floor of 
the fourth ventricle. It has a close relation to the root of the facial, which runs 
along its mesial side (V/Ia), curves round it eventually, and appears to receive 
some fibres from it, but it is doubtful if this is really the case (Gowers). The fibres 
of the nerve run in bundles obliquely ventralwards and downwards (caudalwards) to 
emerge at the lower border of the pons. Between this nucleus and the median 
groove, along the middle of the fourth ventricle, is an oval bundle of nerve fibres 
(fig. 50), which mns longitudinally upwards for about 5 mm., and occupies 
nearly the same position with regard to the nucleus of the sixth nerve that the 
longitudinal fibres which cover the hypoglossal nucleus occupy with regard to the 
origin of that nerve. The bundle in question is the ascending part of the root 
of the seventh nerve (p. 61), and when followed upwards in sections its fibres are 
seen to turn sharply outwards and ventralwards, and to become the issuing root of 
the facial. From the nucleus of the abducens, nerve-fibres pass to join the pos- 
terior longitudinal bundle, and in this they run upwards to the mid-brain, where as 
Duval and Laborde have shown they join the issuing oculomotor roots of the oppo- 
site side. This crossed connection between the third and sixth nerves explains 
those cases of lesion of the pons in which paralysis of the external rectus muscle 
of one side is accompanied by that of the internal rectus of the opposite eye. 

Course of nerve-fibres from the spinal cord upward through the medulla 
oblongata and pons. — ^Assuming for convenience of description the existence of 
three white columns of the spind cord on each side, the various parts of these are 
continued upwards as follows : — 

The posterior column is continued in the medulla oblongata as the white sub- 
stance of the funiculus gracilis and funiculus cuneatus. The longitudinal fibres 
appear to end by terminal arborisations in the grey matter which forms the nuclei ; 
and numerous deep arched fibres enter or emerge from the same collections of grey 
matter, passing through the raphe from the other side of the medulla, where they 
are continuous with the longitudinal fibres dorsal to the pyramids which form the 
main tract of the fillet (Edinger) (interolivary layer of Flechsig). The solitary bundle 
and the " ascending " root of the fifth morphologically represent, as their mode of 
development from ingrowing nerve fibres shows, parts of the postero-lateral column 
of the cord. 

Some fibres also pass from these nuclei, especially from the outer or large-celled 
cuneate nucleus directly into the restiform body of the same side. 



A large part of the lateral colujnn of the cord, viz., the lateral pyramidal tract, 
passes into the opposite pyramid of the bnlb and proceeds in this and ia the 

Fans I 

Medulla ollcngata 

The hemisection was on the left side of the corj, uid wae complete. The section outlines drawn lo 
scale with a camera lucida. Tlie degenerated 6bres ahowu by black data. Those in the eectlDii of the 
lumbar cord are descending, all the rest are Bscending. pg, pyramidal tract ; d.a-l, descending antero- 
Jutersl tract ; d.a,.c, doreo-lateral ascending cerebellar tract ; d.a'.e' (in Pune lU.), degeneration of 
fibres of this tract in the white matter of the cerebellar worm ; v.a.e, Tentrolatcrdl aeoending cerebellar 
tract; v'.it'.c' {in Pons II. and 111.), degenerated fibres of this tract passing doraally into the Tain of 
VieuBsens (in Pons III. ) and into the white matter of the vermis (Pons II.) ; n.///., n. V., n. VI., %. VII., 
issuing librGD of tbe 3rd, 5th, 6th, and 7tli nerre-roott ; v.IV., 1th ventricle. 

ventral part of the pons towards the crusta (see fig. 24, p. 30). Togtsther with the 
small part of the anterior column of the cord which also enters into the constitution 


of the pyramid, it there forms the pyramidal tract of ths isthmus of Flechsig 
(peduncular tract of Meynert;. Some of the fibres of the pyramid, however, emerge 
as external arcuate fibres, and joining the restiform body pass to the cerebellam. 
Moreover, the pyramidal tract is larger in the pons and medulla oblongata than in 
the spinal cord, for as it passes downwards it gives off numerous fibres to end by 
terminal ramifications in the nerve-nuclei of the efferent cranial nerves. Collaterals 
also pass off from the fibres of the pyramids, and even more numerously from the 
longitudinal fibres of the posterior and lateral areas of the medulla oblongata and 
pons to end by terminal ramifications in the grey matter (Kblliker). A part of the 
lateral column of the cord forming the dor so-lateral cerebellar tract (see fig. 52,, 
passes at about the middle of the medulla oblongata obliquely backwards in the 
restiform body to the cerebellar worm. The veniro-latei'al ascending cerebellar tract 
{v,a.c.) passes into the upper part of the pons and turning dorsally at about the level 
of the exit of the fifth nerve curves backwards and enters the cerebellum over and 
along with the superior peduncle and in the valve of Vieussens. 

The rest of the lateral column runs up dorsal to the olives and contributes to 
form the longitudinal fibres of the reticular formation. These are continued through 
the dorsal parts of the encephalic isthmus towards the corpora quadrigemina and 
optic thalamus. Some of the fibres become collected as they pass up towards the 
pons into the well-marked flattened bundle of fibres (fillet) lying dorsal to the 
pyramid. For the fillet is not, according to Edinger, wholly formed of the arched 
fibres which emanate from the nuclei of the contra-lateral posterior columns ; it 
receives an accession of fibres which have already crossed over in the spinal cord 
from the posterior horn (through the anterior commissure), and have passed up the 
antero-lateral column to the medulla oblongata. According to Flechsig and v. 
Bechterew the fillet also contains fibres which are passing from the ventral auditory 
nucleus through the trapezium to the inferior corpora quadrigemina. 

The anterior column of the cord in part is continued into the pyramid of the 
same side, but chiefly dips under the pyramid and forms the longitudinal fibres of 
the white reticular formation in the dorsal part of the mesial area. These pass 
upwards towards the isthmus cerebri. In the pons Varolii one tract of them 
becomes collected into a well marked fasciculus {posterior or dorsal longitudinal 
bundle^ figs. 53, 54,^./), and some of the others join the fillet ; their further destina- 
tion will be afterwards noticed. In the region of the medulla oblongata they are 
indistinguishable from one another in the adult, but in the foetus they are found to 
develope at different periods and are then readily differentiated (Flechsig). 

A small bundle of fibres of the anterior column of the oord was described by SoUy as 
passing obliquely upwards below the olive, to join the restiform body (see fig. 30, /). This is 
seldom distinct. 

Transition from tlie pons Varolii to the mid-brain. — In sections through 
the upper part of the pons (fig. 53) the fourth ventricle, which here becomes rapidly 
narrowed, is roofed over by the two superior peduncles of the cerebellum which are 
passing to the mesencephalon, and by the superior medullary velum and lingula, 
which lies between them. The grey matter of the floor of the ventricle (central 
grey matter) shows on either side near the median groove a group of nerve-cells con- 
tinuous below with the nucleus of the funiculus teres, and above with the nucleus of 
the aqueduct. More to the side is the mass of pigmented nerve-cells known as the 
substantia ferruginea (fig. 53, ^./.), and still more laterally at the angle which the 
roof makes with the floor, a column of large spherical scattered cells, along the 
outer border of which a well marked white bundle — the descending root of the fifth 
nerve (v,d,) — runs downwards towards the middle of the pons where it issues with the 
motor root. These cells and the fibres of the descending root can be traced upwards 



as far aa the superior corpora quadrigemina. Between the central grey matter and 
the reticular formation on either side of the raphe is the now sharply defined dorsal 
(posterior) longitudinal bnndle (p.!.). The tibrep which compose this, which receive 


Rather more than twice the natniaJ size. ' 

p, tnnBTene Gbrea of the pone ; py, py, bnmlles of the pjijuniiis ; a, boundaiy line between the 
tdgmSDtBl pert of the pons and ite TeDlral part ; I', oblique fibres of the lateral fillet, paasuig towtmls the 
inferior corpora quadrigemina ; I, lateral ; P, mesial fillet ; f.r., fonaatio reticulam ; p.i., ponlflrior 
longitadinol bttadle ; i.c.p., superior eerebellar peduacie ;, Bupetior mcdullarj velum ; I, grey 
matter of the lingnla ; i> 4, fourth ventricle ; in the gref matler which bounds it luterally are eeen, 
e.d., tiie descending root of the fifth nerve, with ita nucleus ; (./., substantia femigiaea ; y.c, group 
of mIIk continuoos with the nncleus of the nqncduct. 

their myelin sheaths very early, sen'e partly as a medium of communication between 
the nucleus of the sixth nerre and the third and fourth nerves, and are partly pro- 
longed downwards towards the spinal cord and upwards towards the optic thalamus. 

Pig. 64. SECTION iCHOSa 


IV, isniing fourth nerve ; 
in the Take of Vieutsens ; 
a central grey msttei of the 

root of the fifth nerve ; 
dinal bundle; r, reticular 

I.c.p, superior cerebellar 

Ag, aqueduct of Sj 
ir, ita bundles decus 
IV, a bnndle cut acioe 
aqueduct ; d. V, descending 
p.l, posterior (dorsal) 
formation \ I, lateral 

The fillet is also now more distinct from the neighbouring longitadinal bundles of 
the reticular formation, and a considerable part of it, known as the Meral filht, is 
seen to be passing to the aide of the pons, where ita Gbrea as they course obliquely 
towards the corpora quadrigemina overlap the superior cerebellar peduncle of the 
game side. As the fillet thus passes gradually to the side it gives place to a round 

' The details of this and of several of the preceding figorei are filled in under a Bomswbat higher 
magni^ng power than that lued for tracing the outlines. 



bundle of longitudinal fibres, which begins to be distinct in this region, and which 
passes upwards to form the mesial "bundle of the crusfa (mesial fillet). The superior 
cerebellar peduncle as the sections are traced upwards is seen gradually to shift 
ventral- and mesial wards until in sections through the lower part of the mesen- 
cephalon it reaches the raphe, and decussates with its fellow of the opposite side. 

In sections through the upper part of the pons the fibres of the middle peduncles 
which arch upwards as before mentioned, are cut obliquely, and their entrance 
into the cerebellar hemisphere is no longer seen. The pyramidal bundles are more 
scattered and also more numerous than in the lower part, and the grey matter 
between them is increased in amount. In the highest sections this grey matter is 
beginning to accumulate ventral to the lemniscus and reticular formation, and to 
contain a considerable amount of pigment in its cells (commencement of substantia 
nigra of mesencephalon). 


Baflrinskl, B., Ueher den Ursprung und den centralen Verlauf des Nervus aeusticus des 
/Caninckens u, der Katzej Sitzungsber. d. Berliner Akad., 1886 and 1889, and Virch. Archiv, 1890 ; 
Zur Kenntniss det Verlaufea der hinteren jyurzd des Acugticus, <t*c., Arch. f. Psych., Bd. xxiii., 1891. 

V. Bechtere'w, W., Ueber die Ldngafasei'zUge derformatio reticularis viedullce obLongatoe etpontis, 
Nearol. Gentralbl. 1885 ; ,,VfUer8uchungen iiber die Schleifenschicktf Berichte der Kgl. Sachsischen 
Gesellsch. der Wissensch., Math.-Physik. Klasse, 1885 ; Ueber cine bisher unbekannte Verbindung der 
grossen Oliven mit dem Orosshim, Neurol. Gentralbl., 1885 ; Ueber die innere Abtheilung des Strich- 
korpers und den cushten ffim-nervenj Neurol. Gentralbl., 1886 ; Ueber die BestandiheiU des Corpus 
restiforme, Archiv f. Anat. u. Phys., Anat. Abth., 1886 ; Ue^er die Trigeminusicurzdny Neurolog. 
Gentralbl., 1887 ; Zur FrageOber den Ursprung des H&merven und iiber die pkysiologische Bedeutung 
des N, vestibularis, Neurolog. Gentralbl. 1887 ; Le cerveau de Vhomme dans ses rapports et connexions 
intimes. Archives slaves de biologie, t. iii., 1887 ; Ueber centrale Endigungen des Vagus und fiber 
die Zusammensetzung des sogen. Fasciculus solitarius (Russian), Abstract in Neurolog. Gentralbl., 
1888 ; Zur Frage U. d. Stria: meduUares, dtc, Neurol. Gentralbl, 1892. 

BlTunenau, L. , Ueber d, dusseren Kern des Keilstranges ivi verldngerten Mark, Neurol. Gentralbl. , 
No. 8, 1891 ; JBinige Bemerkungen ueber d. duss. Kern d. Keilstranges, Neurol. Gentralbl., No. 19, 1891. 

Bmoe, A., On the connections of the inferior olivary body, Proc. of the Royal Society of Edinburgh, 

Darkacliewitsoli, Ue. d, Ursprung u. d. centralen Verlauf d. N. access,, Arch. f. Anat. u. 
Fhys., Anat. Abth., 1885. 

DarksohewitBoh, Ij., u. Freud, S., Ueber die Beziehung des Strickkorpers zum Hinterstrang 
und Hinterstrangskem nebst Bemerkungen iiber zwei Fclderder Oblongata, Neurolog. Gentralbl., 1886. 

Dees, O., Ue. d. Ursprung u. d. centralen Verlauf d. Nervus accessorius, Allg. Zeitechr. f. JPsych., 
Bd. xliii., 1887 ; Ueber die Beziehung d. N. accessorius z, d. Nn. vagus u. hypoglossus, ibid, xlix., 1888 ; 
ZttrAnat. u. Phys. d, Nervus vagus, Arch. f. Psych, xx., 1888, and Neurol. Gentralbl., 1888. 

Edinffer, L., Zur Kenntniss des Verlauf es der Hinterstrangfasem in der Medulla oblongata und 
im unteren Kleinkimschenkel, Neurolog. Gentralbl., 1885 ; Vorlesungen U. d. Bau d. Centralnerven- 
tystem, Leipzig, 1889. 

TlechBig', Panl, Ueber die Verbindung der Hinterstrdnge mit dem Gehirn, Neurolog. Gentralbl., 
1885; Zur Lehre vom centralen Verlauf der Sinnesnerven, Neurolog. Gentralbl., No. 23, 1886. 

Xlechsiflr u. Hoeel, Die Centralwindungen ein Centralorgan der Hinterstrdnge, Neurol. 
Centndbl., 1890. 

Porel, A., Ueber d, VerhaUniss, dtc, Ursprung des IX., X., u.^XlI. Himnerven, Festschr. f. 
NSgeli n. KolUker, 1891. 

Freud, S., Zur Kenntniss der Olivemvnsckenschicht, Neurolog. Gentralbl., 1885; Ueber den 
Ursprung des N. aeusticus, Monatsschr. f. Ohrenheilkunde, xx., 1886. 

Gxidden, H., Beitrag z. Kenntniss d, Wurzeln d. Trigeminusnerven, Allg. S^tschr. f. Psych., 
Bd. xlviiL, 1891. 

Hess, O., Das Foramen Magendii und die Oeffnungen an den Recessus laterales des vierten 
Ventrikels, Uorpholog. Jahrbuch, x., 1885. 

Hill, A., The grouping of the cranial nerves, Brain, vol. x., 1888. 

HolUs, W. Ainslie, Some points in the histology of the medulla oblongata, pons Varolii, and 
eerehdlum. Journal of Anat. and Physiol., vols. 18 and 19. 

Hoxn6n, E. A., Ueber seeunddre Degeneration im verldngerten Mark u. Riickenmark, Arch. f. 
patbol. Anat., Bd. Ixxxviii., 1882. 

Jelcrersma, G-., Ueber die Nuclei arciformes, Gentralbl. f. Nervenheilk., 1889. 

Xaasander, G-., S. radios dorscUe del nervo ipoglosso, dsc, Anat. Anz., 1891. 

Xooh, P. D., Untersuchungen iiber den Ursprung und die Verbindungen des Nervus hypoglossus, 
Archiv f. mikrosk. Anat., Bd. xxxi., 1887. 

V. Xolllker, A., Derfeinert Bau des verldngerten Markes, Anat. Anzeiger, 1891. 

^ See also Literature of cerebellum and of origin of cranial nerves. 

F 2 


ZiOwenthal, K., DiginiratlonB teeondaires <iaeendantet dans le bufhe raehidien^'daut U potU 
et VUage tupirieur de Vitthne, Revue m^ic&le de la Suisse romande, v., 1885. 

Marohi, V. , Sopra un caso di doppio incrociamento dei fatci jjiramidaiit Archiv. ital. per le 
malad. nervos., xxii., 1885. 

Mendel, Ueber das aolitdre BUndd, Arch. f. Psyckiatrie, zv., 1884 ; Ueber den Kemurtprung 
des AugenfacialiSt Deutsche medic. Wochenschr., Jahrg. xiii., 1887. 

Meyer, P., Beitixig zur Lehre der Degeneration der ScMeife^ Archiv f. Psychiatrie, Bd. xvii- 
1886 ; Ueber ein FaU von Pons-Jidmorrhagie mit tecunddren Uegenerationen der Sehieifiy Arch. f. 
Psych., xiii., 1882. 

Mlnffazzini, G-., Intorno alia fina anatomia del nudeua arciformis, <bc,, Attl della B. Accad. 
medica di Roma, Anno xv., 1889 ; Intorno aUe origine del n, hypoglonstUf Ann. di freniatria, ii., 1891. 

V. Monakow, Zur Kenntniss d. **du*seren Acustieuskerns ** u. d. Corpus rettiforme^ NeuroL 
Centralbl., 1882 ; and in Archiv f. Psych., Bd. xiv., 1883 ; Experimentdle Beitrdge zur Kenntniu der 
Pyramiden- und Schleifen-bahn, Correspondenzblatt fUr Schweizer Aerzte, 1884 ; Neue experimenteVe 
Beitrdge zur Anatomie der Schleife, Neurol. Centralbl., 1885 ; Strict acusticce u. untere SckUife^ Arch, 
f. Psych., xxii., 1890. 

Pal, J., Ueber d. Veiiauf der Fibrcc arcuaice extemce anteriores, Arbeiten a. d. Instit. f. allg. n. 
xp. Pathologic, Wien, 1890. 

Boiler, C, Der centrale Verlauf d. N. access, ^ Zeitsch. f. Psych., 1881 ; Ueber die Schleife^ Arch. 
f. mikr. Anat., Bd. xix., Neurol. Oenti-alb. 1890. 

Sala, L., SuW origine del nervo acusticOf Monitore zoologico italiano, 1891 (French in Archives 
ital. de biol., t. xvL, 1891). 

Spitzka, E. C, Contributions to the aruUomy of the lemniscus^ Medical Record, 1884. 

Sutton, J. B., The lateral recesses of the fourth ventride; their relation to certain cysts and 
tumours of the cerebeUumj and to occipital meningocele. Brain, 1886. 

Tooth., H. H., and Turner, W. A., Study of a case of bulbar paralysis, uitJi notes on the origin 
of certain cranial nerves^ Brain, 1891. 

VeJas, P., Experitnentdle Beitrdge zur Kenntniss der VerbindungtbaJine des KUinhims und des 
Verlauf s der Funiculi gra^iles und cun-eati, Archiv fUr Pyschiatrie, xvi., 1885. 

Vinoenzi, L., Note histologigue sur V origine rielle de qudques nerfs ciribraux. Arch. itaL de 
biologic, 1884. 

Virchow, H., Ueber die Strioe acusticoB des Menschen, Verhaudl. d. phys. Gesellsch. zu Berlin, 
Arch. f. Anat. u. Physiol., 1888. Physiol. Abtheil. 

Werdriff, Q., Canerement in der rechten Substantia nigra Soemmeringii mit auf- und absteigender 
Degeneration der Schleife und theilweiser Degeneration des Hirnschenkdfusses, Wiener med. Jahr- 
bUchor, Bd. viii., 1889. 

Wilder, Burt G-., Notes on the foramina of Magendie in Man and the Cat, Journal of Nervous 
and Mental Disease, vol. xiii., 1S87. 



The cerebellmn (fige. 55, 5G, and 58) consiBta of two lateral fiemispkeres joined 
together by a median portioo culled, from the peculiar appearance caused by the 
transverse furrows or ridges upon it, the wcrrm or vermiform process. This is seen 

OBWHOiTi, (From Sappey after 

Hirachfelil and LsTeiUi!.) | 
1, 1. inferior vermifDrm pro- 
cess ; 2, 2, median depreseiaa or 
vallecula ; 3, 3, poBtero-iofcrior 
iobe of tbe hemisphere ; 4, taajg- 
lUla ; 5, flocculus ; 6, biventral 
lobe ; 7, pone Varolii ; 8, middle 
peduncle of the cerebellum ; 9, 
medalla oblongata ; 111, 11, ante- 
rior part of the great faoriioptal 
fiasuie ; 12, IS.smallerandUi^er 
I'oota of the fifth pair of nerrea ; 
14, sixth pair ; ]5, facial nerve ; 
16, pare intermedin ; 17, auditor; 
nerve ; IS, gloeao-pharyngeal ; 
19, pDeumo-gastric ; 20, spinal 
accessory ; 21, hypoglossal nerve. 

on the under surface in the fossa between the hemisplieres aa a well-marked pro- 
jection named the inferior worm, but above forms only a slight elevation, the 
euperior worm. In birds, and in animals lower in the scale, this middle part of the 
cerebellam alone exists, and in mammals it is the first part to be developed and to be 
marked off into aabdivisions ; moreover, in most mammala it forms a large median 
lobe very distinct from the hemispheres. 

The cerebellnm occupies the posterior fossa of the cranium. Its median portion 
lies behind tbe 4th ventricle and behind and below the corpora quadrigemina, to 

«-) i 

The medulla oblongata is cut 
acroB near the pons Varolii ; and 
the latter has been sepaiateil 
Bomeirbat from the cerebellum in 
order to bring inlo view tbe pos- 
terior medullary velum. To dis- 
pla; this better the amygdals 
have been remared. 

/ ft, horimntal flaaore ; p », 
poBtero-snperiar lobe ; p i and n, 
poslero -inferior Inbe ; g, slender 

lobe ; b 1, bivflutral lobe ; /, flocculus ; « to n, inferior vermiform process, on which are, c, tubeJ* 
valvuls, p, pyramid, u, uvula, n, nodule ; p v, on each side, placed on the cut surface where the 
amygdalte have been removed, pointa by a line to the Uteral part of tbe inferior (posterior) medullary 
velum ; its median part is lost under the nodule; v, v, cavity of the fourth ventricle ; the cavity 
extends on each side into the lateral recess ; ni, cut surface of medulla oblungala ; V, VI, roots of the 
fifth and sixth cranial nerves- 

ffbich it appears suspended by its superior peduncles. Below and at the sides it 
receives the inferior peduncles (restiform bodies) from the medulla oblongata, and 


&om the anterior part of each hemisphere the thick mass of the middle peduncle 
passes forwards and inwards into the pons Varolii. Between the two superior 
peduncles and behind the upper part of the 4th ventricle ia a white lamina con- 
tinuoue with the white centre of the worm, which thins off into it. Tbia is the 
siiperwr (or anterior) medullar;/ velum or valve of Vieussens ; it extends as far as 
the corpora quadrigemina, filling up the interval between the superior pedimclee. 


and becoming continued into the roof of the aqueduct of Sylvius. Below, there is 
a similar white lamina prolonged under and on either side of the nodule from the 
white centre, and stretchinp; over this part of the ventricle towards its lateral 
boundaries (fig. 56, ^i v). It does not, however, extend far down, but ends with a 
somewhat thickened mai^in, concave do\vnwardB, being prolonged towards the 
calamus scriptorius roerelj by the ventricular epithelium, which covere its ventral 
surface. To the semilunar lamina thus formed the name inferior (or posterior) 
medullary velum is applied. 

The hemispheres are separated below and behind by a deep notch {posterior 
cerebellar rwkh, intisura marsupialit), and above and in front by a bnwder, shallower 
notch (anUrior cerebellar notch, ineisura semilunaris). The upper vermiform process, 
although slightly elevated, is not sharply marked off from the dorsal surface of the 
hemispheres, so that the upper surface of the oi^an, which is on the whole flattened 
but somewhat ridged in the middle (aiimen monticuli), slopes downwards uninter- 
ruptedly cu each side aud behind {clivwi). On the inferior surface each hemisphere 
is convex both from before backwards and from side to side, but is separated 
from ita fellow by a deep median fossa, named the vallecula, which ia continuous 
behind with the posterior notch, and in which the inferior vermiform process 
(fig. 56, c to n, fig. 58 B, i.v. to n.) lies concealed. Into this hollow the medulla 
oblongata is received in front, and the falx cerebelli behind. 


The greateet diameter of the organ is transverse, and extends to about four inches 
(10 centimeters) : its greatest width from before backwards is about two inches (5 
centimeters) : of the middle part about one inch and a half (4 centimeters) ; and 
its greatest depth is about two inches, but it thins out towards the lateral border. 
It weighs about 5 oz. 

The cerebellum is characterised by its laminated or foliated appearance, its 
surface being everywhere marked by deep, closely set, transverse and somewhat 
curved, fissures, which extend a considerable depth into its substance, but do not all 
entirely encircle the organ, for many of them coalesce with one another, and some 
of the smaller furrows have even an oblique course between the others. Moreover, 
on opening the larger fissures, other folia are seen to lie concealed within them, not 
reaching the surface of the cerebellum. 

The depth of the fissures can best be estimated in sections through the organ 
taken across the laminae : in such sections each lamina is seen to have a white 
centre and a grey cortex, and the white centres of the laminae appear in the form of 
processes ramifying from a larger white centre near the middle and anterior part of 
the organ : to the arborescent appearance thus obtained in section the name arhor 
vitx cerebeUi has been applied. 

Externally the most conspicuous fissure is the great horiiontal flssare (figs. 
56, 58, fh), which beginning in front at the middle peduncle of either side 
extends round the outer and posterior border of each hemisphere, dipping down into 
the posterior notch. This fissure divides the cerebellum into an upper and lower 
portion, corresponding in fact to the upper and lower surfaces, in each of which 
several lobes, separated by fissures for the most part deeper than the rest^ are 
described. Taking the great horizontal fissure to divide the cerebellum into an 
upper and a lower half or surface, we may first consider the parts which are present 
upon the upper surface and which compose the upper half of the organ in both the 
worm and the hemispheres. 

UPPER SUItFACXi. — The upper worm begins at the superior medullary velum 
between the two superior peduncles and ends at the bottom of the posterior notch in 
a short, concealed transverse lamina, termed the folium cacuminis. It is usually 
described as being formed of five successive parts or lobules, which are termed from 
before back the lingula^ the central lobe, the culmen (culmen monticuli), the clivua 
(clivus monticuli), and the folium cacuminis. Corresponding with these in each 
hemisphere are the large postero- superior lobe, continued laterally from the small 
folium cacuminis, the posterior crescentiCy continued from the clivus, the anterior 
crescentic lobe, continued laterally from the culmen, the ala lobuli centralis^ continued 
from the central lobe, and sometimes a lateral extension of the lingula. 

Of the fissures which separate these lobes of the upper surface from one another, 
four in number, the first, or most anterior, which may be termed the precentral 
sulcus, lies in front of the central lobe, and separates it from the lingula. The 
next, or post4:entral sulcus, divides the central lobe and its alae from the culmen 
and anterior crescentic lobes. The third, or preclival fissure (also called the antero- 
superior), separates the culmen and anterior crescentic from the clivus and posterior 
crescentic lobes. Lastly, the fourth, or posiclival fissure (also called the postero- 
superior), lies immediately over the folium cacuminis, and separates this and the 
postero-superior lobes from the clivus and posterior crescentic. Below the folium 
cacuminis and the postero-superior lobes comes the great horizontal fissure which 
has been already described. 

Besides these interlobar fissures, all of which extend deeply down towards the 
centra] white substance, there are certain other sulci which on the upper surface 
of the hemispheres are almost or quite as well marked as the interlobar ones, but 
which are less deep or are not seen on the upper worm. They are best made out in 


vertical Bcctions of the hemisphere. Two of these intralobar fiBBoreB occor in the 
posterior cresceatic (clival) lobe and one or two in the anterior crescentic (cutmi- 

Kg. 68.— Vrsws of thb uppib (A) iiro lohir (B) si 


In A. l.B, lobulna centralis; a.l.e, ala lobuli centralis; m, culniea monticnli ; I.m, lobas 
animinis ; d, olivue ;, lobus cliTi ; f.coc, lobus cacuminiB ; l.t, tobuH bnberig ; ».p.-c, Bulcun poat- 
centraliB ;, sulcus precllTalu ; i.p.-cl, aulcas postcliTalis ; /.A, f.k, fissura hocuontalis magna. 

In B. I, linguU ; l.c, lobnlns centralis ; a.l.e, ala lobuli ccotralis ; i p--c, anicus poatceDtralU ; 
v.m.i, Telnm medullars euperius ; p.g.c, pedunculue cereb«lli Buperior ; p.c, pedunculi cerebelli mediaa 
Bt Inferior ; n, noduloe ; u.m.i, velum medullare icferius ; pjl, peduDCuIus flocculi ; j(, flocculus ; u, 
nmla ; am, omjgdala ; pg, pjramia ; t.biv, lobus biTentralis ; (.ti, tuber Talvulffi eeu posticum ; '.(, 
lobm pMtero-inferior ;', lobulns giacilia anterior ; i.yr^, lobulus gracilis posterior ;, tmlous 
pregmcilii ; ».i,-gr, aulcua intra-gracilis ; ',p,-ffr, sulcus poetgracilis ; f.h, Sasiira boriioDtalis magna. 

The vallecola baa been somewhat opened out to displaf the parta of the lower worm. 

nate) (fig. 59). The lamioee and fissurea of the upper surface all have a suhparallel 
tmnsverse direction, corving forwards as they traverse the hemisphere to lose them- 
Bclves at the anteto-Uteral border in the great horizontal fissure. 


Lobes of the upper surface. — ^We may now describe in detail the subdivisions 
of the upper surface, taking (since they are directly continuous with one another) 
those of the worm and hemispheres together. 

The lingnla. — ^This is usually confined to the worm, and from the surface it is 
entirely concealed by the next lobe : it is best seen in a median section of the organ 
(figs. 57 and 69). It consists of a small tongue-shaped group of four or five trans- 
verse laminas, which may be said to lie upon the middle of the superior medullary 
velum (fig. 68, I). Its medullary centre is in continuity with the velum, and 
forms part of the roof or dorsal boundary of the fourth ventricle which here has a 
tent-shaped projection into the middle of the cerebellum (fig. 57, 4). 

The lingula gradually shades off at the sides and is usually unrepresented in the 
hemispheres, but its laminse are sometimes prolonged laterally for a little distance 
over the superior cerebellar peduncle {frenulum lin^tdce). 

The central lobe and its al». — ^The central lobe is largely concealed by the 
culmen when the cerebellum is in its natural position, but when the organ is cut 
away from the adjacent structures this lobe is seen in the anterior notch, where 
its laminBB appear at the surface. They are prolonged beyond the limit of the wonu 
for some distance along the upper and anterior part of the hemispheres, where 
they fonn wing-like continuations of the central lobe which are known as the 
akB loluli centralis (fig. 58). The central lobe receives a primary branch of the 
arbor vitas which passes upwards and forwards into it from the enlargement of 
the whit« centre which is known as the trapezoidal body, but the fissures (^r^- 
cmtral and postcentral) which separate it from the lingula and culminate lobe 
respectively, are not better marked at the surface than those which intervene 
between the laminse of the culminate lobe, and, as a glance at the sections (fig. 59) 
shows, its laminaB all belong to the same (ascending) group of folia as those which 
constitute the culminate lobe. 

The cnlmen and anterior crescentic lobes : lobns cnhninis. — The culmen 
occupies rather more than half of the upper surface of the worm, and, as its name 
implies, constitutes the most prominent part of the upper worm. Its surface shows 
three or four well-marked lamellae, beset by a number of secondary and tertiary folia. 
It is separated from the next part of the worm by a deep groove which descends to 
the middle of the organ ; this sulcus is prolonged, as we have already seen, on to 
either hemisphere, having there been termed the antero-superior sulcus, and passing 
in a curved manner parallel with the general disposition of the laminse on this sur- 
face to the antero-lateral margin, where it runs into the anterior part of the great 
horizontal fissure. The antero-superior sulci together may conveniently be termed 
the preclwal. The subdivision of the hemisphere which is cut off between this 
precUval fissure behind and the postcentral sulcus in front has been known as the 
anterior crescentic lobe {lobtcs lunatus anterior, KoUiker). The two anterior crescentic 
lobes, together with the culmen with which they are in complete lateral continuity, 
form a main subdivision of the upper surface of the cerebellum, which may appro- 
priately be termed the lobe of the culmen. The lateral parts of the lobe each receive 
three well-marked branches of the medullary centre of the hemispheres ; in the 
central part they come off by a common stem from the corpus trapezoides of the 
worm (fig. 59). 

The divns and posterior crescentic lobes: lobns clivi. — Behind the 
antero-superior or preclival fissure, and extending as far as the folium cacuminis 
(from which it is separated by the postero-superior or postclival fissure), is another 
considerable group of laminae which receive their branches from the upper aspect of 
the horizontal stem of the arbor vitae. In a median section of the worm these 
laminae appear to form one group with the folium cacuminis and the laminae of the 
tuber valvulae (fig. 59 A), and this group has been described by Schwalbe as con- 


stituting a posterior lobe. In fact, however, the great horizontal fiasure below the 
folium cacaminiB and the postclival fissure above this folium separate the group 
into three well-marked divisions, of very unequal size it is true in the worm, owing 
to the rudimentary character of the central or cacuminate division, but far more 
distinct and equal in the hemispheres ; they may therefore be conveniently thus 
subdivided in the worm also, and of them, two (the clivus and folium cacuminis) 
belong to the upper worm, the third, tuber valvulae, to the lower. 

Two or three secondary laminae of the clivus reach the surface of the worm, but 
they are beset with many tertiary folia, and other important folia belonging to the 
same group lie concealed in the preclival fissure. 

The lateral extension of the clivus on to each hemisphere is known as the 
posterior crescentic lobe {I, lunatus posterior^ KoUiker), and the two posterior 
crescentic lobes with the clivus between them, bounded in front by the preclival, 
behind by the postclival fissure, may collectively be termed the lohe of the clivus. 
The lateral parts of this lobe each receive two or three primary branches of the 
medullary centre of the hemisphere (fig. 59). 

The combined anterior and posterior crescentic lobes of each hemisphere were formerly 
termed the quadrilateral lobe. 

The fblimn cacnmixiui and postero-snperior lobes : lobne cacnmiiiis- 

— The folium cacuminis is formed by the extremity or apex of the main horizontal 
stem of the arbor vitae vermis (figs. 57, 59). As the vertical section shows, it is 
composed of but a single primary folium, which may be either plain or beset 
with rudimentary folia. But at the side of the worm it rapidly expands, with 
divergence of its bounding fissures and a great increase of size of its main branch of 
the arbor vitae and the formation of numerous secondary and tertiary folia, a large 
lobe being thereby produced at the posterior and upper part of each hemisphere 
which has been termed the postero-stiperior lobe. The expansion occurs mostly 
above the horizontal plane, and its branch of the arbor vitas has a direction no longer 
directly backwards, but rather upwards and backwards ; this upward shifting 
appears to be due to the great development of the lobes of the lower surface of the 
hemisphere. The postero-superior lobes are bounded, like the folium cacuminis itself, 
in front and above by the postclival fissure, below by the great horizontal fissure ; 
joined as they are in the middle line by the folium cacuminis, they form a great 
winged mass which occupies the posterior third of the upper surface of the cerebellar 
hemispheres, and forms the rounded postero-lateral border ; to this conjoined mass 
the term lobus cacuminis may be applied. 

ITNjy^B, SUItFACE. — Turning now our attention to the under surface of the 
organ, we here meet with considerably greater complexity, and the correspondence 
between the parts of the worm and those of the hemisphere is less clearly apparent. 
The lower worm extends from the inferior medullary velum to the folium cacuminis 
(great horizontal fissure), and the parts or lobules which are enumerated in 
it are four in number, viz. : from before back (1) the nodule, (2) the uvula^ 
(3) the pyramid^ and (4) the tuber valvulcc seu posticum. On the hemisphere a 
greater number of lobes are distinguished, viz. : (1) the flocculus, corresponding 
with the nodule ; (2) the tonsil (amygdala), coiTesponding with the uvula ; 
(8) the birventral lobe, corresponding with the pyramid ; (4) the slender lobe^ formed 
of an anterior and a posterior part well marked off from one another ; and (5) the 
inferior semilunar lobe, which also shows a tendency to subdivision. This 
last lobe corresponds with and is directly in lateral continuity with the tuber 
posticum of the worm. The slender lobes are interpolated in the hemisphere, and 
have not any obvious prominence of the worm corresponding with them, but they 
appear to represent a development of certain rudimentary folia which are seen in 


sagittal sections of the worm on the lower part of the stalk of the tuber valvnlae, 
entitely concealed by the pyramid (see fig. 59 B). If this is the case, then the com- 
bined slender and inferior semilunar lobes may be reckoned as collectively forming 
a primary subdivision of the hemisphere, corresponding with the tuber posticum 
of the worm and to which the term postero-inferior may be applied,* and the two 
postero-inferior lobes, together with the tuber valvulse which unites them in the 
middle line, may collectively be spoken of as the Jobus tuberis. This large lobe 
occupies at least two-thirds of the inferior surface of the cerebellum ; of the re 
maining third more than one-half is occupied by the combined pyramid and biven- 
tral lobes, about one-third by the uvula and amygdalsB, and the small remaining 
portion by the nodule and flocculus. 

Fuisnres of the under sur&ce. — The lobes of the under surface of the 
organ are separated from one another by fissures extending deeply into both the 
worm and hemispheres. In the worm there are three such interlobar depressions, 
viz. : one between the nodule and the uvula (postnodular), one between the uvula 
and pyramid {prepyramidal), one between the pyramid and tuber valvulse (post- 
pyramidal), besides the middle of the great horizontal fissure separating the tuber 
valvulae from the folium cacuminis. In the hemispheres a larger number is 
apparent. The posinodular sulcus passes laterally into a groove curved with its 
convexity forwards which first limits the amygdala in front and then passes between 
the flocculus and biventral lobe to join the anterior end of the great horizontal 
fissure. The /^e/7yram«!^Z sulcus curves laterally round the outer side of the 
amygdala, separating it from the biventral lobe : it joins the postnodular in froDt 
of the amygdala. From the sides of the postpyramidal sulcus three deep fissures, 
concentric with one another, curve outwards and forwards over the under surface of 
the hemisphere. The most anterior of these, and also the shortest, passes at first 
more forwards, concealed by the amygdala before curving round in the manner 
described. It lies between the biventral and slender lobes, and may be termed the 
anterior arcuate or pregracile sulcus. The second of the three concentric fissures 
subdivides the slender lobe into two nearly equal parts (lobulus gracilis anterior and 
lobulus gracilis posterior) ; we may distinguish it as the middle arcuate or mid* 
gracile. The third, which is the longest, separates the slender lobe from the 
inferior semilunar lobe ; like the other two it arises at the mesial edge of the hemi- 
sphere opposite the depression (postpyramidal sulcus) between the pyramid and the 
tuber valvulse, and arches round on the lower surface of the hemisphere with its 
concavity forward to fall into the great horizontal fissure at the antero-lateral margin. 
This fissure may be termed the posterior arcuate or postgracile. Behind this 
again there is a fairly well marked deep fissure, serving to subdivide the inferior 
semilunar lobe. This may be termed the htver or lesser horizontal sulcus. Lastly, 
the deep antero-posterior grooves which mark off the lower worm may conveniently 
be termed the sulci vallecula (dexter et sinister). 

Lobes of the under enrfikce. — The lobes of the under surface of the organ 
as ah-eady enumerated may be now more particularly described in order from before 

The nodnle and floconlns: lobns nodnli. — The nodule occupies much the 
same position relatively to the inferior medullary velum and tent of the fourth 
ventricle that the lingula occupies with regard to the superior medullary velum, but it 
is usually better developed than the lingula. Although sometimes merely composed 
of a few transverse laminae set upon the median part of the inferior medullary velum, 
it more often appears as a distinct prominence having a separate branch of the 

' In the previotiB edition of this work, the term poetero-inferior was used as a synonym for the 
inferior semilunar lobe. 


ai'bor vitBB (fig. 59 A), It can only be seen after the cerebellum is separated from 
the medulla oblongata and pons, or in a median section, being almost entirely con- 
cealed by the uvula when the organ is viewed from below. The lateral part of 
the inferior medullary velum is continued on either side of the nodule as a thin 
white semilunar band with a thickened concave free lower border (fig. 58 B, r.m.i). 
Traced laterally towards the hemisphere, the white lamella becomes thickened and 
covered with gi*ey matter {pedunculus flocculi), and at length expands into a small 
irregular lobule lying in the groove between the biventral lobe and the middle 
peduncle of the cerebellum, and composed of a few short irregular laminae, which 
tend to diverge from the attachment of the stalk. The nodule, with the inferior 
medullary velum, the stalk of the flocculus, and the flocculus itself constitute 
collectively a small but distinct subdivision of the cerebellum {lobtis noduli). 

Other small portions of laminated grej matter sometimes occur attached to the floccnlns, 
usually lying between it and the middle peduncle. These have been termed aceeuary 

The nvnla and tonsils: lobns nvnl». — The uvula forms a considerable 
j portion of the lower worm, being elongated from before back ; three considerable 

secondary laminae, beset with eight or more tertiary folia, appear at the surface. 
It is least prominent close to the nodule, and from this part it enlarges rapidly 
downwards and backwards to attain its greatest prominence next to the pyramid. 
Like the nodule and the pyramid it is purely a median prominence, being separated 
from the hemispheres by the deep groove (sulcus valleculae) which prolongs the 
vallecula on either side of this part of the worm. At the bottom of this groove 
on either side of the uvula is a low corrugated greyish ridge which connects the 
narrow stalk of the uvula with the stalk of the tonsil : this concealed connecting 
ridge is known as the furrowed hand. From its outer extremity the rounded 
amygdala projects downwards and backwards into the vallecular groove, concealing 
the sides of the uvula mesially, and the narrow connection between the pyramid 
and biventral lobe posteriorly. The uvula, furrowed band and tonsil constitute col- 
lectively another distinct subdivision of the hemisphere {amygdalo-uvular lobe, lohus 
uvuIcb), The amygdala or tonsil forms a rounded projection of about 10 or 12 
folia, which run nearly in a sagittal direction, so that in a sagittal section of the 
cerebellum passing through the tonsil, its branch of the arbor vitae appears expanded 
and not obviously dendritic (fig. 59 C). Above and in front it has a few transverse 
laminse which are only seen in sections, being concealed, in the natural position of 
the parts, by the rest of the projection. Opposite the inferior medullary velum 
its white matter comes for a certain distance to the surface, covered, of course, by 
pia mater. The amygdala is lodged in a depression (nidus avis) at the front of the 
vallecula, which is bounded by the uvula mesially and the biventral lobe laterally ; 
the surface which rests against the uvula is nearly smooth, as is the corresponding 
concave surface of the uvula ; a continuation of the postnodular sulcus separates 
it from the inferior medullary velum. 

The pyramid and biventral lobes : lobns pyramidis. — The pyramid forms 
the most marked prominence of the lower worm, but as seen from the surface, it 
shows only three or four transverse laminae. It is in reality a long clavate projection 
attached to the stem of the arbor vitae by a narrow stalk, and it is not only separated 
from the uvula and tuber valvulsB by deep fissures, but also from the hemispheres 
by the sulcus vallecul» on either side of it. Its connection with the biventral lobe 
of the hemisphere is here maintained by a low narrow ridge, which joins the stalk 
of the pyramid with the mesial pointed extremity of the biventral lobe. This 
connecting ridge is evidently analogous with the furrowed band of the preceding 
lobe, but it is an even less distinct structure. To see it the amygdala must be 


removed, or a vertical section made through the organ, passing just to the outer 
side of the pyramid. The biventral lobe is roughly triangular in shape, with 
the base forwards abutting on the postnodular sulcus, and the apex directed 
backwards and inwards towards the root of the pyramid. The outer side is 
bounded by the outwardly curved pre-gracile fissure, the inner by the side of 
the vallecula, but is concealed by the amygdala, which projects over the lobe. 
The JaminsB have a curved direction radiating from the apex towards the base of the 
triangle. The lobe is partly bisected by a fissure (midventral) deeper than the 
rest, and becoming better marked towards the base. This fissure divides the lobe 
into an inner and an outer portion ; from this subdivision its name has been 
derived. Collectively, the pyramid, the connecting ridges, and the biventral lobes 
constitute a distinct division of the cerebellum, to which the name hhe of (he 
pyramid may be applied. 

The tuber posticnm and postero-inferior lobes : lobus tnberis. — The 
tuber valvulsB sen posticum, which constitutes the hindermost division of the inferior 
worm, exposes about five or six tertiary folia (laminae transversales inferiores) at 
the surface between those of the pyramid and the folium cacuminis. It differs 
from the other constituents of the inferior worm, and resembles those of the 
superior worm in being obviously prolonged laterally into and gradually enlarging 
to form the corresponding hemisphere lobes (fig. 58 B, Lv^ Li), These conjoined 
postero-inferior lobes of the hemispheres with the tuber valvulae of the worm 
collectively foim a large alate mass {lobics tuberis), bounded in firont by the 
anterior arcuate or pregracile fissure, which separates it from the pyramidal 
(biventral) lobe; behind by the great horizontal fissure, which also limits it 
antero-laterally. Its laminae run in a curved manner, concentrically with these 
fissures, and it is separated into four crescentic parts by three concentric fissures 
two deep and complete, the middle arcuate and the posterior arcuate and a third 
only slightly less deep, the lesser horizontal fissure. Of these four parts the two 
anterior, about equal in size, form what has been termed the slender lobe (lobus 
gracilis) ; the two posterior, of which the hinder one is the larger, together form 
what has been termed the inferior semilunar lobe. 

The whole cerebellar worm may thus be regarded as subdivided by deep sulci into nine 
parte or lobes, each of which has a corresponding lobe of the hemisphere continuous with it. 
This continuity is obvious upon the upper and posterior aspects of the organ, but on the inferior 
aspect it tends to be rudimentary and is moreover concealed within the sulci vaUeculsB. The 
combined lobes which are thus formed by the continuity of the lobes of the worm with those 
of the hemispheres are as follows : — (1) lobus lingulas, (2) lobus centralis, (3) lobus culminis, 
(4) lobus clivi, (5) lobus cacuminis, (6) lobus tuberis, (7) lobus pyramidis, (8) lobus uvulse, 
and (9) lobus noduli. The hemisphere-parts of the lobus lingulss and of the lobus centralis 
are rudimentary, but otherwise the hemisphere-parts of the lobes are considerably larger than 
those of the worm, in some cases, as in that of the lobus cacuminis and the lobus tuberis. the 
difference of size being very great. The former (lobus cacuminis) is, in fact, represented in 
the worm by a single concealed folium only, while a large portion of the lobus tuberis, viz., 
the lobus gracUis, can hardly be said to be represented in the worm. These nine lobes are 
separated from one another by interlobar fissures, which are all nearly equally weU marked in 
the hemispheres, whilst in the worm some are less developed, particularly those above and 
below the folium cacuminis. This median part of the lobus cacuminis is, therefore, 
imperfectly marked off from the clivus above and the tuber valvulae below, the three together 
forming a very distinct posterior subdivision of the worm. 

The relations between the parts of the worm and those of the hemispheres, and the fissures 
which separate the several lobes from one another, as well as those which serve to subdivide 
the lobus tuberis, are indicated in the accompanying table : — 



DlAGBAMMATio TABLE to show the corresponding parts of the worm and hemispheres and 
the fissures which separate them into lobes. The positions of the principal intra-lobar 
fissures of the hemisphere are marked bj thin lines. 





Sulcus precentralis. 

Frssnulum lingulad Lingula 

Sulcus postcentralis 

Sulcus preolivalis 

Sulcus postclivalis 

Sulcus horizontalis ) 
magnus 3 

Sulcus postgracilis 

Sulcus intragracilis . . . 

Sulcus pregracilis ) 
8. postpyramidalis j 

Sulcus prepyramidalis . . . 
Sulcus postnodularis . . . 

Ala lobuli centralis Lobulus 















Lobus lingnlas 

LobuB oentrallB 

LoboB oulminia 

Lobus divi 

Lobus caouminis 





anterior 3 


Lobulus «D* 

gracilis 5* 
posterior *^ 



I«obus tuberis 










Xobus pyraznidis 

Lobus nvulsB 

Lobus nodnli 

Description of the arbor vit» cerebeUi.— When a section is made through 
the wonn or through either hemisphere across the direction of the folia, the organ'^is 
seen, as already mentioned, to be composed of a white or medullary centre and of a 
uniform cortex of grey matter, and the section presents a dendritic appearance 
(arbor vitse cerebelli) in consequence of the fact that the larger laminse are them- 
selves formed of secondary, and these again are beset with tertiary folia. It is 
only in such sections that the relative depth and importance of the fissures can be 
estimated, and a description of the sections is therefore fully as important as that 
of the surface-markings, and is in fact necessary for the elucidation of the latter. 

The mode of transition of the parts of the worm into those of the hemispheres 
can also best be made out by the inspection of successive sagittal sections ; 
beginning with a median section through the worm, and passing gradually to the 
side, the successive sections being made in planes parallel with the median plane, or 
only so far inclined to it, and to one another, as to cut the majority of the lamellce 
at right angles. 

1. Section of ths cerebellum in the median plane of the worm (fig. 59 A, and 
fig. 57). In front we notice the tent of the fourth ventricle projecting with a 
sharp angle into the enlargement of the white substance known as the c(n^i8 
trapezoides ( The apex of the angle is directed backwards with a slight down- 
ward tilt, so as to leave only a thin layer of white matter— the middle part of the 
inferior medullaiy velum— between it and the nodule. The corresponding layer of 


white matter between the cavity of the fourth ventricle and the lingula is the 
middle part of the superior medullary velum. The two vela are prolonged like roots 
upwards and downwards from the anterior or ventral side of the corpus trapezoides. 
Rrom the upper part of the corpus trapezoides two branches diverge, one upwards 
with a slight inclination forwards^ this is the branch to the central lobe ; the 
other, the thickest and strongest of all the branches of the arbor vitse of the 
worm, passes upwards and backwards into the culmen. This stem of the culmen 
gives off secondary branches on cither side. Of (hose which are directed upwards 
and forwards, the one nearest the base is rudimentary, and enters a small lamina 
concealed at the bottom of the post-central fissure : the next two are large, and 
enter laminss which reach the surface, but before attaining it they may themselves 
fork. The prolongation of the stem also reaches the surface, being first bifurcated, 
but the branches from the lower or posterior side of the stem of the culmen, two, 
three or more in number, pass into short laminae which mostly lie concealed within 
the pre-clival fissure. 

Prolonged backwards from the postero-inferior angle of the corpus trapezoides 
is a narrow horizontal stem, which after a course of about two centimeters, ends 
directly in the medullary centre of the folium cacuminis, often passing round a 
slight curve just before reaching this. From the upper side of this horizontal stem 
about five branches pass upwards and backwards, and from the lower side about 


lu the Diagrammatic Table on p. 78 the designationB " lobulus gracilis 
anterior" and "lobulas gracilis posterior" should be transposed. 

it gives off a vertical branch which passes into the upper part of the lobe nearest 
the culmen, bifurcating near the surface, and is then continued on in a nearly 
horizontal direction parallel to and overlying the folium cacuminis. 

Of the branches from the lower side of the white centre and its horizontal pro- 
longation three are of great importance. The foremost one passes from the corpus 
trapezoides almost vertically downwards for about six or eight mm. into the uvula, 
giving off only small lateral branches ; it then gives off successively two or three 
branches which course downwards and forwards, usually bifurcating before reaching 
the surface. Only short branches are given off backwards from the main part of the 
uvula stem. 

About two or three mm. behind the branch to the uvula, that to the pyramid 
passes off. This has a general direction downwards and backwards ; it gives off 
lateral branches as it proceeds, most of which are small, but one or two longer 
branches come off on its anterior aspect and pass to the surface nearly vertically 

Following the horizontal stem back, two or three rudimentary offshoots are seen 
entering small lamellse which are concealed within the postpyramidal fissure, until 
finally, about 15 mm. from the corpus trapezoidea and 5 mm. from the base of the 
folium cacuminis, another considerable branch passes off at an acute angle, with a 
curve forwards and downwards into the tuber valvulas. Its lateral oflfehoots, which 
are at first short, become gradually longer, corresponding with the expanding form 
of this lobe of the worm. 

The deepest fissures of the median section are the precentral, the postcentral, 
the preclival, the prepyramidal, the postpyramidal, and the postnodular (see 
fig. 59 A). The postclival fissure is here quite shallow, the great horizontal only 
slightly deeper. The general grouping of the branches of the arbor vitse is into 


twice tha natural tilt. (Prom pbotographB, ) 

A, mediim section of tbe worm. 

B, section near the edge of the <rorm at the tnuuiUoo iulo th« hemuphen. 

C, St the edge of the hemisphere. 

D, throngh the middle of tbe hemisphere. 



five divisions (irrespective of the white matter of the hngula and nodule), viz., two 
ascending (central lobe and culmen), a posterior group (clivus, folium cacumiais, 
and tuber valvulae), and two descending (pyramid and uvula). 

2. Arbor tntm at transition of worm into hemisphere (fig. 59 B). With the 
general enlargement of the organ as the worm passes into the hemisphere the white 
centre becomes greatly increased in amount. This aflPects all parts of it, but first 
and most markedly the corpus trapezoides and the root of the branch into the 
culmen, which is here a large square mass of white matter from which three distinct 
branches pass towards the upper surface of the culmen, which is subdivided by two 
deep fissures (anterior and posterior intraculminate) into as many parts. A short 
branch also passes forwards from the corpus trapezoides into the ala lobuli centralfB. 
The lingula is still seen in this section, and the superior medullary velum is 
becoming thickened by the fibres of the superior cerebellar peduncle. The 
horizontal stem of the arbor vitae is also much thicker, and from it the branches 
of the clivus pass upwards as two main stems, which go towards the surface, 
bifurcating as they approach it ; there are concealed folia in the pre- and post- 
clival fissures. The postclival fissure is now deep, as is also the great horizontal, 
and between the two a lobe, fan-shaped in section (the postero-superior), is now 
visible, having a distinct large bifid branch of the arbor vitse directed upwards and 
backwards into it, each ramus dividing more than once before reaching the surface. 
Between the great horizontal and the postpyramidal fissure a large branch passes 
downwards and backwards, and gives off several well-marked rami from its lower 
border, three or more reaching the surface. The branch into the pyramid is broader 
at its root ; in fig. 59 B, the section passes outside the uvula, and has taken a slice 
off the amygdala. 

8. In a sagittal section altogether beyond the vermis and fust within the limit 
of the hemisphere, what in the worm constitutes the horizontal stem of the arbor 
vitae, has become greatly enlarged, and has now blended with the enlarged corpus 
trapezoides to foim the large central white mass of the hemisphere (fig. 59 C). 
In this the nucleus dentatus is now seen, and appears as a thin irregularly triangular 
wavy band of grey matter, with the blunt apex of the triangle directed posteriorly 
towards the horizontal fissure and the open base looking forwards and receiving the 
great mass of fibres of the superior cerebellar peduncle which now replaces the 
superior medullary velum. Above the level of the horizontal fissure seven or eight 
principal processes of the white centre extend into the lobes of the upper surface : 
the most anterior is small, and passes forwards into the diminishing ala lobuli 
centralis ; three enter the anterior crescentic lobe (in the section here figured they 
still appear to come off from a common stalk) ; two or three, the posterior crescentic ; 
and a large branch directed obliquely upwards and backwards passes into the 
postero-superior or cacuminate lobe : between these principal branches are a few 
rudimentary ones passing into concealed lamelte, of which there are groups at the 
bottom of the pre- and postclival fissures. Besides the postcentral and the pre- and 
postclival fissures, two other fissures divide the anterior crescentic lobe into three 
parts, and other fissures divide the posterior crescentic. The cacuminate lobe is not 
thus subdivided by complete fissures. 

Below the level of the great horizontal fissure six or seven main branches come 
off from the white centre. Two of these pass into the inferior semilunar lobe ; 
one, the posterior, being very large and bifid or trifid ; one passes into each division 
of the lobus gracilis, one into the biventral lobe, and a broad anteriorly directed 
branch into the amygdala, A seventh small ofishoot, directed almost due forward, 
belongs to the stalk of the fiocculus. In sections still further outwards (fig. 59 D) 
the conditions are much the same as here described, except that the ala lobuli 
centralis, and the amygdaloid branch are no longer seen, and the branch into the 


bireatral has become distinctly bifid. The nuclenB dentatus does not extend far 
into the lateral part of the hemiaphere, and the Buperior cerebellar pednncle is no 
longer cat ; bnt fibres are seen streaming from the white centre of the hemisphere 
into the middle and inferior peduncles. The general conformation of the section 
is somewhat altered, bat the number and relations of the sub-divisiooa of the 
hemisphere is not materially different, and the several branches of the arbor vitro 
and the more important fissnres are readily recognizable. 

Knolsi in the wliite matter of tlie oereballiuii. — The dentate atiolens 
(corpus ciliare, corpus dentatum) of the cerebellum {figs. 59 C, and 60, n.d.), very 

pig. eO.— Sectios Aciujsa t 

n.rf., nuclem dentatus u 
ilenUte nneieoB ; i.c.p., con 
croauiig in the mecliaa vbite matter. 

similar to that already described in the olivary body of the medulla oblongata, 
presents the appearance of a waved line of compact yellowish brown substance, 
containing white matter within. The wavy character is more apparent in horizontal 
than in vertical sections through the hemisphere. The line is interrupted at its 
anterior and mesial part {hilum), where the superior cerebellar peduncle emerges 
from it. The dentate nucleus may be described as consisting of a plicated pouch or 
capsale of grey substance open at one pait and enclosing white matter in its interior. 
like the dentate nucleus of the lower olivary body. 

In addition to the corpus dentatum certain other portions of grey matter, which 
have been only more recently recognised, are found in the white centre of the 
cerebellum (Stilling). They are three in number on each side and are termed 
respectively the nucleus emboliformis, nucleus globoaus, and nucleus fastigii (figs. 60, 
61). The nnoleiut embolifomiis is a small clavate mass of grey substance lying 
inesially to and partly covering the hilnm of the dentate nncletis. On the inner side 
of the nuclens emboliformis, between it and the middle line, is a streak of grey 
matter passing antero-posteriorly and ending behind in an enlai^d extremity. Tbiu 
has been named the nnolena globosos. Finally, close to the middle line, where 


it is only separated from ita fe)low bj a narrow septum of white matter, IB a ratber 
larger portion of grey substance, which lies in the anterior part of the white centre 
of the worm, and close to the npper wall of the tent-like projection in the roof ot 
the fourth Teotricle. It ia termed the nnclmu of tlt« roof or iraclmis fiwtisu. 


(PrDiD Henle, after Stilling.) } 
The section is taken jnat over the roof of 
the fourth Teotrinle. The nuclei are lepre- 
iietiteil lighter than the white niatter id which 
they are embedded. 

C d, corpus dentatiim ; X, nucleas emboli- 
fonnia ; ;, j, nucleus globoKus ; z, nncleiu 
fustigii. Abore the two coalesced mof-nndei 
are Been some of the libree of the SDperior 
(anterior) decussation, and aboye these again 
the laminw and furrows of the Itngula (Lg) ; 
whilst below the roof-nuclei one or two 
Uminffi and fnrrowB of the inferior Tennifonn 
procesa are included in the aection. Ccq, 
Boperior cerebellar peduncle. 

These several portions of grey matter 
are not entirely isolated, but are 
connected here and there both with 
one another and with the dentate 

The structure of the corpiis den- 

latum resembles that of the olivary body. Stellate cells Tr'scth to ysW^h inch 

(6fi to lOfi) in size, lie in grey matter which is traversed by bandies of nerve-fibres, 

passing in varions directions but chiefly from without inwards. 

The niwleue emboliformie agrees closely in structure with the nucleus dcDtatus, to 

whioh it seems to bear the same relation as do the accessory olivary nuclei to the 

and nucleus globosus differ somewhat i 
lefly in the much larger size of their cells, 
ilar to thoHe of the nucleus of Deiteis in 

chief olivary nuclena. The nudeutfasiigii i 
stmctnre fh>m the dentate nucleus, and chie 
which, according to Meynert, are very simili 
the medulla oblongata (see p. 56). 

CommiiBitral fibres in the wMte nutter of tba cerflbellam. — Two chief 
sets of deaissaiing commissural fibres were described by Stilling in the middle line of 
the cerebellum ; one at the superior part of the worm at the base of the central 
lobnle— tt< si^erior commissure (fig. 60, com') ; the other at the inferior part 
(m/erwr commissure (eom")). Commissural fibres also pierce the nuclei of the 
roof. In addition to these crossing fibres, which connect tJie two halves of the 
white centre, other association fibres connect one lamina with another, passing 
in the white substance of the laminae across their general direction, and arching 
round the fissures between the lamina. 

FsAuttolwi of til* cerebellum. —The cerebellar peduncles are constituted by 
white fibres which pass ont from or into the white medullary substance of the 

The superior pedundes {crura ad cerebrum) emerge from the opper and mesial 
part of the mednllary substance of the hemispheres, and run upwards and forwards 
towards the corpora qnadrigemina, under which they eventually pass and thus dis- 
appear from the surface. They are situated at first at the side, but subsequently in 
the roof, of the npper part of the fourth ventricle. These peduncles are concealed 
by the upper part of the cerebellum, so that to see them properly this must be 


divided in the middle line and tnmed aside. When thia is done the enperior orara, 
with the Buperior medullarj velum stretched out between them, are brought into 
view. Their further course in the mid-brain will be subsequently traced. 

The fibres of the saperior peduncle pass almost entirely out of the interior of the 
dentate nucleus (intraciliar fibres), but some fibres curve round the outer side of thia 
without passing into it (eitraciliar), and some of the mesial fibres are traceable 
directly into the white substance of the worm. Probably many of the fibres of 
these peduncles which emeige Irom the dentate nucleus m« connected with its cells, 
bnt others pass in bundles through the grey lamiaa which composes it, without 

Fig. 62. —PioDRi BHOwma the thkkb pitrb 

Sappey after Hincbfeld and Leveille.) 

On the left side the Ihrea cBrebeUttr pe- 
duDclsB have been cut ehort ; on the right 
Hide the hemiBphere haa been cut obliqueJy 
to show its conneclJDn with the superior and 
inferior peduncles. 

I, median groove of the fourth veDtricle ; 
2, the same groore at the place where the 
aaditory striiE emerge from it to croM the 
floor of the lentriole ; 3, inferior peduncle 
or reatiform bodj ; 4, funiculus gracilis ; 

5, superior peduncle ; on the right aide the 
disaectiao du>vt the Huperior and inferior 
{■eduDclcs crossing each other an the; paoa 
intfl the white centre of the cerebeQum ; 

6, fillet at the side of the orurs cerebri ; 

7, lateral grooiee of the crura cerebri ; S, 
corpora quadrigemjna. 

being thus connected. They appear to go eventually to the superficial grey matter 
of the lamins. 

From the superior medullary velum longitudiual fibres can be traced passing into 
the white centre of the worm. These are chiefly fibres belonging to the antero- 
. lateral ascending cerebellar tract (see pp. 25 and 65). 

Many, if not most, of the fibres of the aaperior peduncle oripnate in oella within the 
cerebellum, and underg'o degeneration as the reealt of lesions of that organ (Bee p. 93). But 
in a case, reported by Mendel, of leaion of the left thalamus opticna, a well-marked bundle of 
degenerated fibres was traceable through the tegmentum of the left side mesial to the nnolens 
t^meati, acroas to the tig'lit side at the decnssation of the superior peduncle*, and along the 
outer side ol the right superior pednaole to the tight hemisphere. 

The middh peduneUs (crura ad pontem), distinguished by the small size of their 
fibres, comiug from the pons Varolii, enter the lateral part of the white matter in two 
main bundles. One of these, composed of the superior transverse fibres of the 
pons which pass obliquely downwards over the others (fig- 80, 0' radiates into 
the lateral and lower parts of the medullary centre of the hemispheres. The 
other bundle, which is formed of the lower transverse fibres of the pons, is joined 
at its passage into the white centre by the restiform body or inferior peduncle 
(fig. 30, A), and the fibres of both turn upwards and radiate into the upper parts 
of the medullary centre of the hemisphere, and partly into the upper part of the 
worm (but most of the pons fibres enter the hemisphere). Those peduncular 
fibres which pass into the worm are derived chiefly from the restiform body, and 
include the large fibres of the dorso-lateral cerebellar tract, most of which go to the 
same side but some pass across to the opposite side. Those which enter the hemi- 
sphere curve over the corpus dentatum, and are termed by Stilling the semicircular 
fibres (fig. 60, s). They come mainly fixim the opposite olivary through the resti- 
form body. A small part of the fibres of the restiform body is said by Stilling to 
end in the corpus dentatum. 


The fibres of the middle peduncle^ when traced ventralwards into the pons, 
reach the middle line and there undergo decussation. After this intercroBsing 
many of their fibres appear to end in the grey matter which is so abundant in 
the ventral part of the pons (nuclei pontis, fig. 49, n.p.). A certain number of fibres, 
however, take a sagittal direction in the raphe and pass towards the reticular 
formation, where they appear to give fibres to the posterior longitudinal bundle ; 
by which means a direct connection seems to be established between the cerebellum 
and the nuclei of the third, fourth^ and sixth nerves (Mingazzini). 

The inferior peduncles (crura ad medullam) issue from the white matter of 
the lateral hemispheres, between the other two, and pass forwards immediately 
outside the superior peduncles to reach the lateral wall of the fourth ventricle. 
Here they turn sharply downwards, at a right angle, and become the restifonn 
bodies of the medulla oblongata. 

The restiform body consists of several sets of fibres having a distinct 
origin, and obtaining their medullary sheath at different periods of develbpment. 
These fibres are as follows : — (1) Fibres of small size derived from the contra- 
lateral lower olives. These, which are the last to become medullated, are seen 
passing as arched fibres through the corresponding half of the medulla oblongata 
and across the raphe to enter the hilum of the opposite olivary nucleus. After 
passing through the band of grey matter, whether joining its cells or not is not 
certainly known, these fibres appear to pass longitudinally upwards in the reticular 
formation of the medulla oblongata and pons, and in the tegmentum of the cerebral 
peduncle, and thus to reach the cerebral hemisphere without again crossing : 
ultimately they are in all probability connected with the cerebral cortex (? of the 
psychomotor region only). The existence of this connection may probably explain 
those cases in which atrophy of one of the cerebral hemispheres, especially of the 
psychomotor region, has been found associated with atrophy of the inferior olive of 
the same side and of the restiform body and cerebellar hemisphere of the opposite side. 

(2) Fibres which emerge from the adjacent cuneate nucleus (especially its outer 
portion), and perhaps also from the gracile nucleus, and pass directly into the resti- 
form body of the same side. These fibres may represent a bulbar ascending 
cerebellar tract homologous with the dorso-lateral cerebellar tract of Flechsig which 
is seen in the spinal cord, in which case the outer cuneate nucleus may very probably 
represent Clarke's cell-column of the cord. 

Aooording to some authorities, the restiform body also receives a contribntion through 
the arched fibres from the contra-lateral nucleus gracilis and nucleus cuneatus. 

(8) Fibres of the dorso-lateral ascending cerebellar tract of Flechsig, which are 
traceable along the whole length of the cord from the lumbar region upwards, and 
which pass into the restiform body, and through this mainly into the same side of 
the worm. 

(4) Fibres of the descending cerebellar tract (see p. 25) which, after removal 
of the cerebellar hemisphere, undergo degeneration down the whole length of the 
antero-lateral column of the cord near its periphery (see p. 32, and fig. 71, A, B, C). 

(5) Fibres which are passing to or are derived from the root of the auditory nerve 
and perhaps others to or from some of the other cranial nerves (see p. 93). 


Each lamina of the cerebellum has a central part or core of white substance 
which is an offshoot (secondary or tertiary) from the white centre of the organ, 

^ Our knowledge of the actual relationship of cells and nerve-fibres in the cerebellar cortex has been 
only quite recently entirely remodelled, owing to the introduction of the method invented by Golgi, and 
its fruitful application firstly by Golgi himself and subsequently by Bam6n y Cajal. 


and a cortex of grey matter conaisting of two layers, an inner and oater, the latter 
being covered snpCTfioially by pia mater. Between the inner and outer layers of 
grey matter is an incomplete stratum of lar^ nerve-cells, the corpuscles of Purkinje. 
Tbe fibres of the white matter are medallated, and are disposed in bundles which 
have a parallel course as tbey pass fitim the principal of&boots of the white centre 

a, pU mater ; b, exUrnal layer ; «, layer of 
corposcles of Parkiaje ; d, timer or granule 
U;er ; e, modollarj centre. 

of the oi^an into the secondary laminie. 
This parallelism is maintained in tbeir 
passage through the centre of the 
laminte, but tiie fibres gradually turn 
off obliquely into the grey matter, so 
that the white core gradually thins off 
towards the extremities of the lamina. 
Owing to the turning outwards and 
pass^e into the grey matter of these 
bundles of white fibres, the white core 
is not sharply marked off under the 
microscope from the grey cortex ; but 
it is more distinctly marked off at the 
bottom of the fissures which separate 
the laminEe than in the laminGe them- 
selves. As the fibres pass radially into 
the grey matter they lose their parallel 
arrangement, and tend to branch 
amongst the small nerve-cells of the 
adjacent inner layer of the grey matter ; 
many pass through this and end in the 
axis-cylinder processes of the cells of 
I'urkinje, whilst others pass beyond 
these cells into the outer or " mole- 
cular " layer of the grey matter. 

The grey matter of the cerebellar - — .^ - 

cortex is disposed, as already intimated, 

in two distinct layers. The inner or granule layer is so called because it contains 
numerous small nerve-cells known as "granules;" this layer has a reddish or 
yellowish-brown colour in tbe fresh condition, hence it is sometimes termed the 
" mst-colonred " layer. The granules are more closely packed in the outer part of 
the layer ; near the medullary centre of the lamina they are separated by the 
entering bundles of white fibres, between which they may penetrate for some distance 
witbin the white centre. Besides small nerve-cells the granule-layer includes a few 
glia-cells. The outer or molecular layer has, under the microscope, a finely punctated 
(molecular) appearance. It is of fairly uniform thickness, whereas the granule-layer 
is thicker near the extremities of the laminae than in the furrows. It contains 
nerve-cells, but they are neither so numerous nor so small as the " granules " of the 
inner layer, many nerve-fibres, mostly running parallel to the surface, and also a 
number of fibres which run vertically to the surface {Bergmann's fibres), and end 
below the pia mater. These fibres are derived &om cells which are situated in the 
granule-layer, and which are usually regarded as glia-celta (see p. 92). 


The molecular layer is further in large part occupied bj the dendritic proto* 
plaemic processes of the large nerve-cells which lie at the junctioa of the grannie 
and medullary laycTB, already mentioned as the celUoT corpuacles of Purkmje. These 
are conspicuous fiask-shaped cells, each with a number of ramified protoplasmic pro- 
cesses directed peripherally, and an axis-cylinder or nerve-process which paasee 
centrally into the granule-layer, where it becomes medullated, and passes directly 
into a nerve-fibre of the mednllary centre. As with the axis-cylinder proceaaes of 

Fig. flj. — SiOTiOHB or coRiix OBBIBBLU KtiintD BY Goloi'b vithod. (Bun6n 7 C»jlL) 

I. — SectioD taken acmes the lamina, 

II. — Stwtion mads in ths directioQ of the lamiiui. 

A, outer or molecular lajer ; B, inner or (pvnule lajer ; C, mtdallu? centre. 

a, corpnacle of Furkinje ; b, Bmall gianutes of inner layer \ c, tt iirotopltwinic procesa of a grannie ; 
d, neire-fibre prac«sB of a giannle pasBing into the molecalar lajer, vhere it bifuTcatee uid becomea a 
longitudinal fibre (in I. these longitudinal fibres are cut acioBa and appear as dot£) ; t, bifurcation of 
another fibre ; g, a gracnle lying in the white centre. 

the cells of the cerebral cortex, and, according to Golgi, with those of the anterior 
horn-cells of the spinal cord, these axis-cylinder processes of Purkinje's cells also 
give off lateral ramuscles (oollaterala) which lc»e themselves amongst the granules, 
some turning backwards to enter the molecular layer (figs. 69,70). The protoplasmic 
processes of the cells of Pnrkinje are spread out in planes which nin transvereely to 
the laminee (Stilling), so that they are seen in their full extent, only in sections 
cat vertically to the surface but across the laminse (fig. 64, 1.) ; whereas in vertical 
sections taken parallel to the laminte, the ramifications appear limited to a com- 
paratively narrowed tract (fig. 64, II.). The protoplasmic proceasea (dendrites) may 
arise hy a single root or by two roots ; in either case there is a firequent dichotomoBS 
division, with slight enlargements at the points of division, and also the giving off 
laterally of numerous ramuscles which take a more horizontal course in the mole- 
cular layer than do the principal branches. The branches do not anastomose nor 



join with those of other cells, bnt have free terminationSy often carling back for a 
short distance before ultimately ending. 

Besides these dendritic processes of Porkinje's cells, the molecular layer con- 
tains great numbers of very fine horizontal fibres, running longitudinally as regards 
the laminae. These pass into the molecular layer from the small cells of the granule 
layer. The axis-cylinder processes of the small " granules " in fact pass vertically 
between the corpuscles of Purkinje and enter the molecular layer, where they join, 
by a T- or Y-shaped junction, with one of the horizontal fibres just mentioned 
(fig. 64, XL) ; these fibres may therefore be regarded as the branches of the axis- 
cylinder processes of the granule-ceUs. They appear to end after a short course 
either simply or by slightly ramifying. They are probably not meduUated. 

The nerve-cells of the molecular layer are divisible, according to their relative 
position in the layer, into two kinds, outer and inner. The outer cells, i.e., those 


a, a cell from the outer part of the layer with a horizontally directed branched axis-cylinder prooeas ; 
b, neire-fibre processes of ceUs which send processes c to aid in forming the basket-work d e around the 
cells of Purkinje ; /» a process directed towards the surface of the lamina. 

in the outer half or so of the layer, somewhat smaller than the inner, have extensive 
protoplasmic processes and an axis-cylinder process which extends for some distance 
horizontally or obliquely in the layer, ramifying freely (fig. 65, a) ; its mode of ending 
is somewhat doubtful. The inner cells, called also ** basket "-cells, usually lie near the 
cells of Purkinje, but they may be placed some little distance within the molecular 
layer. Their protoplasmic processes pass in all directions, some of them even 
reaching the surface of the organ ; the axis-cylinder process, which seems not to be 
provided with a medullary sheath, usually emerges from the side of the cell and 
extends laterally for some distance, giving off at intervals, as it passes along, a 
number of vertical branches which pass inwards towards the cell-bodies of Purkinje's 
corpuscles, near which they become considerably enlarged (fig. 65, &, e). Having 


reached these they break ap into a close feltwork of filaments (terminal lamification) 
which Barrounde the corpuscles of Pnrkinje, and with similar ramifications Irom 
other cells, envelopea the corpuscle ia a sort of basket-work of nerre-filamenls. 
This bseket-work extends even for a short distance along the azis-cjUnder process 
of the corpuscle (fig. 66). 

The "granules" of the inner, or rust-coloured, layer of the gtey matter are 
mostly small nerve-cella, nearly spherical, and provided with several small proto- 
plasmic processes, which soon end in close bunch-like terminal ramifications within 
the layer (fig. 64, b). But the axis-cylinder process is of far greater extent, and 
taking a peripheral course, passes vertically beyond the corpuscles of Pnrkinje for 

Fig. 86. — Babut-wore or fibbis AHODicn TWO ciM-a or 
PuBKljrjK, (Ramfin J Cajd.) 
a, anit-tjliader ornerve-Gbre process of one ot the eaipiiicles 
of Forkuije ; b, fibres proloDged over the beginning of thekiia- 
cytindei' proceu ; c, branches of the nerre-fibra proceeMa of 
cells of the nolecular lajer. felted together uronnd the bodiea 
of the corpuscles of Purkinje. 

a variable distance into the molecular layer, where 
. it becomes connected with the horizontal fibres of 
that layer (fig. G4, e) in the manner before described. 
A few of the " granules" are larger ; their cell- 
bodies lie chiefly in the outer part of the granule- 
layer, near the cells of Purkinje. They are somewhat 
stellate, and have long, ramified, protoplasmic pro- 
cesses ; these may penetrate both into the white 
centre of the lamina, and into the molecular layer. Their axis-cylinder processes 
are singularly branched, losing themselves in a ramification which may extend 


A, molecnlw lajer ; B, cells of Porfcinje ; C, grenqic-layer ; D, white substance, 
a, e,/, g, fibrea which end in pleinsea enTeloping the principal protoplasmic proceesea of the cell* 
of Porkii^e ; K on enveloping plezai ; c, bod; of ceU of Purkinje ; m, " moss '' fibres. 

thronghout the whole thickness of the granule>layer j it is not certainly known if 
they are meduUated, nor if they are connected with fibres of the white centre. 


Of the fibres which pass from the vhite centre into the grey matter of the 
lamiDie some, which have already been deBcribed, are the nerve-procesaes of the cells 
of Purkinje. Bat others are derived from the meduUated fibres of the white centre, 
which appear to have two modes of termination in the grey matter. Some of these 
whit« fibres traverse the granule-layer, and, branching within that layer, exhibit 
peculiar moss-tike appendages, both on their ramuacles and at the place whence these 
come off i they have on this acconnt been termed by Ramon y Cajal the " moss- 
fibres" (fig. 67, m). Each'snch fibre, with its ramifications, extends over a con- 
siderable area of the granule-layer, but the 
branching and moss-like efflorescences are 
especially well marked near the level of the 
cells of Purkinje, beyond which they pass 
into the molecular layer, where they appear 
to become longitudinal and horizontal, whilst 
breaking up yet again into fresh branches. 


BLIKEHTB. Oolqi'b METHOD. (Raiii6n y Cajal.) 
a, pi> mftter ; b, procenes of the neuroglia- cells pswiog towards the satfsce wliere thej ead in 
cooickl enlurgementa ; c, e, elongaUd neuroglia-cellB ; d, stellate neuroglia-cell. 

Fig. 69. — Two c>LU or Fokeuji rHOM ihb oibibblluh of a riw-bokh fdppt-, aHuwii bt (Joloi's 
HiTHOD. (lUmdD ; Cajal.) 

A, eaticnlar layer of cerebellam villi insertion of radial fibres. 

B, Itjer of iDperfieial gnuiulea. 

C, molecular lajer showing the tongitudiaal fibres derireil from the granules of the next layei D 
CDt Mrea and appearing ai points. 

D, granolB-lajer. 

a, bodies of Purkinje's cells, the protoplasliiic pracesses of which are still short and very irregular. 

b, nerre-fibrs process of one of the cells j c, d, t«o colhteisls from the same fibre ; e, t, their 
termiDftl arboriuitiana in the molecular lajer. 

The second kind of fibre from the medullary centre (fig. 67, a, e,f, g, fig. Hi,j, n, o, a), 
has been described by the same observer as passing towards the cells of Purkinje, 
and enveloping their principal dendrites in a terminal ramification, or close plexus, 
in the same manner that the bodies or bases of the cells and the commencement of 
their axis-cylinder processes are enveloped in "baskets," formed, as we have seen 
(p. 89), by the vertical branches of the nerve-processes of the inner cells of the 


molecnlar tajer. The cell-origin of the fibres vhich pass from the white centre 
into the grej cortex is entirely unknown, bnt in man; cases it is probably dtnated 
in the spinal cord (see diagram, fig. 20, p. 23). 

Venroglia-oalls. — Lying amongst tiie nerve-cells of the granule-layer which are 
nearest the cells of Putkinje, are a number of relatively large cells (fig. 68) giving 
off dendritic processes which are directed towards the periphery, and which coorse 
through the molecular layer as the fibres of Bergmann before mentioned. From the 
other side of these ceUs other processes pass off and become lost, partly amongst the 
granules, partly amongst the fibres of the white centre. These centrally-directed 
fibres somewhat resemble the axis-cylinder processes of nerve-cells, but the cells ia 
qaestion are usually r^;arded as gUa-cells, belonging, therefore, to the supporting 

Pig. 70. — Tbaksvibbe siciiob of ' 

(Bam6D ; CbJkI.) 

A, epithelinm-like layer of aaperGcial tone ; B, lajer of bcriiontal bipolar calls ; C, laolECulAr 
tajer ; D, granule- Isjer. 

a, epithclinni-like cell ; b, bipoltu boruontal coll ; «, cell sending a procom downwudi into tbe 
molecular layer ; e. /, g, bipolai' vertical cells : A, cell of Purkinje ; i, its nerre-fibrB procem giving off 
a collateral towards the molecular layer ; j, n, o, >, Gbree from tbe white substance passing to form 
pleiusea (I, m) wbich envelop the upper part of the bodies and the praunal part of the dendritei of 
cells of Purkinje ; r, " mose " fibre. 

tissue of the nerve-centre. The peripherally-directed fibres expand at the snriace of 
tbe organ immediately underneath the pia mater into small conical enlai^ements, 
with their bases directed superficially ; here they form a sort of limiting membrane 
similar to the internal limiting membrane of the retina, which is formed by the 
fibres of Miiller. Although many of the neurogUa-cells have this arrangement, 
others, which are stellate in form, lie more deeply amongst the grannies, or amongst 
the nerve-fibres of the medullary centre. 

In fhe embi70mo oerebeUnm and iu most animalB for n few da^e after birtli, Uier« ii a 
layer of gntanle-like cells, several deep, superflcial to the molecular layer. This haa been 
termed by Ramfin j Cajal.the zone of snperflcial frranules, and he lias shown that It is formed 
at a certain stage of development of two distinct stiata, one the more supezfldal composed 
ef epithelium-like elements set perpendicularly to the surface, and the other next to tbe 
molecnlar layer compomd of bipolar oells placed parallel to the surface, and to the dirMAion 


of the oerobellar lamell® Tfig. 70, A, B). Bat the farther deyelopment of these cells has not as 
yet been ascertained, and it can only be conjectured that they become grradoally transformed into 
cells of the molecalar layer, for no sach saperficial zone can be seen in the adalt cerebellum. 
At early stages of development there are also to be seen in the molecular layer, bipolar cells 
placed with their axes vertical, and having protoplasmic processes extending down towards or 
into the rust-coloured layer, and axis-cylinder processes extending towards the surface, and 
beooming continued by T-shaped junctions into fibres running parallel with the processes of 
the horizontal bipolar cells which have just been described. These vertical bipolar cells may 
perhaps be derived from the horizontal ones, and represent a stage in the formation of the 
smaller granules of the rust-coloured layer, but we have no clear evidence as to their further 
course of development. Like the 8ui)erficial granules they also are only found in young 
animals. The cells of Purkinje in the cerebellum of embryonic and very young animals are 
very irregular multipolar cells, with relatively short protoplasmic processes, but a well- 
developed axis-qylinder process, which already has two or three collateral fibres extending 
towards and ramifying in the deeper part of the molecular layer (fig. 69). It is not until two or 
three weeks after birth (in the dog) that the dendrites begin to assume the characteristic form 
and arrangement. The arborescence which in the adult cerebellum envelopes the principal 
dendrites of the cells of Purkinje (see p. 91 and fig. 67), is at this early stage chiefly con- 
fined to the upper part of the body of the cell (fig. 70). 


The degenerations of nerve-fibres which follow lesions of the cerebellum have 
been investigated by Marchi in animals (dogs and monkeys) operated upon by Luciani. 

Eemiextirpatioii (see fig. 71). — After removal of one half of the organ 
extensive degeneration is seen in all three peduncles of the same side ; very little, if 
any, in the peduncles of the opposite side. It may therefore be inferred that none 
of the peduncles contain commissural fibres connecting the two halves of the organ. 

The degenerated fibres in the superior peduncle pass partly to the tegmental nucleus 
of the opposite side, and partly to that of the same side ; in other words, the decus- 
sation of these peduncles in the region of the inferior corpora quadrigemina is not 
complete. Some fibres can be traced as far as the optic thalamus. 

The middle peduncle^ after removal of the corresponding half of the cerebellum, 
is completely degenerated as far as the raphe. Degenerated fibres are seen inter- 
mingled with the pyramidal fibres both of the same side and of the opposite side, 
and with the fibres of the fillet and posterior longitudinal bundle, mainly of the 
same side. Degeneration and atrophy are also produced in the grey matter of the 
pons (nuclei pontis) of the same side. The degeneration in the fillet and posterior 
longitudinal bundle is most marked on the side of the lesion ; it can be followed 
upwards to the region of the corpora quadrigemina, and downwards to a tract at the 
periphery of the antero-lateral column of the spinal cord. A bundle of degenerated 
fibres is also seen passing to the pyramidal tract. These appear to pass upwards 
towards the corpora quadrigemina, and probably to the corpus striatum, chiefly 
of the same side ; a few are traceable downwards into the cord. 

The inferior peduncle^ after hemiextirpation of the cerebellum, is notably 
degenerated in its inner and outer parts. A small degenerated bundle is traceable 
vith the inner arched fibres, across the raphe to the opposite lower olive which 
undergoes complete atrophy ; other arched bundles pass from the restiform body to 
the tract of the fillet, and of the posterior longitudinal bundle of the same side ; 
and from these, as above stated, many degenerated fibres are traceable down the 
periphery of the antero-lateral column of the cord, some down the pyramidal tract, 
but most are situated ventral to the direct cerebellar tract of Flechsig in the 
antero-lateral descending cerebellar tract. 

It is also stated by Marchi that after hemiextirpation of the cerebellum, degene- 
rated fibres are seen passing along with the roots of nearly all the cranial nerves, 
especially the second, third, fifth (ascending root), sixth, seventh, and twelfth, and 


the striae medullares, and along with the anterior roots of the spinal nerves. These 
degenerated fibres are numerous on the same side as the lesion, bnt a few occnr in 
the opposite nerves. Those which pass to the cranial nerves run along the posterior 

Fig. 71. — Odtlink or skot ona s^ovird thb mmiiiihations 

A, lumbar cord ; B cemcal cord C medulla obloDgata D pons Varolii ; £, mid-brsin at nacleni 
ot third nerve. 

Id a and B. the degeneration is in the antero- lateral column of the same side as the losion, eicept io 
B, vhere there is a, little degeaeration on the opposite side. 

In C, a indicates the reBtiform body ; b, the ascending root of the fifth ; e, tiie poeterior longitadinal 
bundle ; d, the aniero- lateral tract ; t, the pTmnida ; f, the olivaiy Ducleos ; g, the fillet ; h, the 
hypoglossal nucleus. 

In D, n is the superior cerEbellar peduncle ; b, the middle peduncle ; c, the poaterior longitudinal 
bundle ; d, the £llet ; t, the antero-lateral tnct ; /, the rapbe. 

In E, a is the nuclena tegmenti (moat degeneration in the crosbed superior cerebellar peduncle) ; 
h. the iesuing fibres of tbe third nerve ; d, the posterior longitudinal bundle ; e, the cnuta ; /, part of 
the fillet. 

longitudinal bundle, those which pass to the spinal nerves down the descending 
antero-lateral tract of the cord. 

Extirpaitioii of worm. — After h em i -extirpation of the middle lobe only 
of the cerebellum the degeneration in the superior peduncle is comparatively 
slight, and entirely crosses at the decussation to pass to the t^mental nocIeuB of 
the opposite side. The degeneration of the middle peduncle is most marked 
ill the upper third of the pons ; but little occurring in the lower two-thirds. 


That of the iaferior peduncle is limited to the outer or lateral part of the restiform 
body. A few fibres pass from this across the raphe to the lower olive of the 
opposite side. Others pass as arched fibres to the tract of the fillet, to the posterior 
longitudinal bundle, and through this to the cranial nerve-roots, especially the 
third, fifth, eighth, and twelfth. Others are traceable down the antero-lateral 
columns of the cord, but those to the pyramidal tract are lacking. 


Beohterew, W., Zur AnatonUe der Schenhel des Kleinhims, inahesondere der Brilekenarme. 
Neurolog. Centralbl., 1885 ; Ueber die BettandtheiU des varderen Kleinhimstidst Neurolog. Centralbl., 
1887, and Arch. f. Anat. u. Fhys., Anat. Abth., 1888. 

Beevor, Oh.. E., Die Kleirihimrinde, Arch. f. Anat. u. Physiol., 1883. 

Bellonoi, G>. e Stefanl, A., Contribuzione cdV istogenesi deUa corteceia cerebeUarey Memoria 
letta air Accademia de Feirara, 1886 : Archives italiennes de biologie. t. xi, 1889. 

Borffherinl, Continbution d Vhistologic normale du cerveUt, Archives itai. de biol., xii, 1889. 

Broflset, J., Contribution d Vitude des connexions du cervelet, Th^ne, Lyon, 1890. 

Cramor, A., Einaeitige Kleinhii'natropkie, (t*c., nebtt einem Beitrag z, AncUomte der Kleinkirn' 
MticU, Beitrage zur pathol. Anatomie, Bd. xi., 1891. 

Fosaxi, SulV origine delle fibre nem^ose nello ttrcUo molecolare deUe circonvoluzioni cerebellari deW 
uomo, Atti della R. accad. delle scienze di Torino, 188S. 

V. Ghehnohten, A., La structure des centres nerveux, La Cellule, t. vii, 1891. 

Golffi, O., JRecherches sur Vhistologie des centres nerveuXj Arch. ital. de biologie, t. iii. et iv., 1882. 

▼. QtLdden, P., Ueber d, Verbindungsbahnen des Kleinhims, Berichte d. deutsch. Nattlrf.-yersamm- 
lung, 1882 (Neurol. Centralbl.). 

▼. Kolliker, A., D<u Kleinhirn, Zeitschr. f. wissensch. Zoologie, Bd. 49, 1890. 

Ijuolani, L., II eervelletto, Firenze, 1891. 

Mairclil, v., Des diginiraiion* consdcutives d V extirpation totale et partielle du cervelet. 
Archives italiennes de biologie, t. vii, 1886. 

Kendel, B., Secunddre Degeneration im Bindeamiy Neurol. Centralbl., 1882. 

MineraBzini, G., Intomo al decorso d. fibre appart al peduncvlus medius cerebelli ed al corpus 
restiforvM, Arch. p. 1. scienze mediche, 1890. 

Obersteiner, H., Der feinere Bau der KUinhimrinde, Biol. Centralbl., Bd. iii., 1885. 

Baxn6n y Cajal, S., Sobre las fibras nerviosas de la capa molecular del cerebdo, Revista 
trimestrial de histologia normal y patologica, 1888 and 1889 ; Sur Vorigine et la direction des pro- 
longations ncrveuses de la coucke moliculaire du cerrdetf Internationale Monatsschr. f. Anat u. 
Phys. , Bd. vi, 1 889 ; Sur les fibres nerveuses de la couche granvleuse du cervelet et sur revolution des 
elements ciribeUeux, Ibid., Bd. vii, 1890 ; Apropos de certains dements bipolaires du cervelet avee 
quelques details nouveaux sur revolution des fibres e^rebelleuses, Ibid., vol. vii, 1890. 

BetziuB, G., Die nervosen Elemente der Kleinhimrinde, Biol. Untersuch. Neue Folge, iii., 1892. 

^ See also literature of Medulla Oblongata and Pons Varolii. 



The parte of the brain next to be described are entirely covered by the cerebral 
hemlBpheres. They comprise the crura cerebri and corpora qnadrigemina, the optic 
thalami with the middle commissnre, and the pioeal body, in addition to the 
following structures which are Been when the brain is removed from the sknll and 
its under-Burface or baae is examined, viz. : — the posterior perforated space, the 
corpora alfoicantia, the tuber cinereum with the infondibulum and pituitary body, 
the optic tractfl and chiaema, and the lamina cinerea. Of these the corpora qnadri- 
gemina and crura cerebri are found in connection with the aqueduct of Sylvius, and 
belong to the mid-brain, while the optic thalami and the other Btructnrea above 
enumerated occur in connection with the third ventricle, and belong to the inter- 

The aqueduct of Sylvioa (iter a tertio ad qnartum ventricnlum) is a narrow 
passage into which the upper end of the fourth ventricle gradually narrows, and 
which in front expands abruptly into the third ventricle, it is rather more than 

Fig. 72.— Sbwiom tbbocoh *h« okioik of tub ^odbih Biav* (Stilling). 

A, tnuitvets« aeotion at the place of emergence of the Derre-fibrea. B, obliqao sectdon cairied along 
tLe conne of the bnndlcB from the DUcleuB of origin to the place of emergence. Aq, Sjlviui aqnedact, 
with its Burrounding grey matter ; IV, the serve •bnnilleB emerging ; /I", decaBsatioD of the nerres of 
the two aides ; IV", a round bandle paaaing downwards b; the aide of tbe aqueduct to emerge a little 
lower down ; n,IV, nncleua of the fonrth nerte. I, fillet ; i. c. p., auperior cerabellsr peduncle ; 
d. 7., descending root of tbe fifth nerve ; pi, poalerior langitudinsl bandle ; r, raphe. 

half an inch long. In shape it varies in different parts, being T-shaped in section 
below (near the fonrth ventricle), triangular above (near the third), and in the 
intermediate part of an elongated oval form, but somewhat shield-shaped in the 
region of the superior corpora quadrigemina. It is lined by ciliated columnar 
epithelium, outside which is a thick layer of grey matter, continuous with that of 
the fourth ventricle. Outside this central grey malter of the aqueduct, the lateral 
and ventral parts (basal part) of the meaencephaloii are compoaed of the thick 
masses of the cerebral peduncles {erura cerebri), whilst the dorsum is formed by the 
lamina guadngemina, so called &om bearing the four mamillated tubereles known as 
the corpora quadrigemina. 

The epithelium which lines the Sylvian aqueduct is ciliated (as elsewhere in the 
ventricles of the brain) and the attached ends of the cells extend as radiating 
ependymal fibres through the thickness of the mid-brain to reach the surlace — at 
least, this can be seen to be so in the embryo and in small vertebrates, and is 
probably also true for all. But some of the ependymal fibres are attached to 
neuroglia cells which occur at various levels in the cooise of the fibres ; they have 


probably been formed by tbe detachment of some of the epithelinm cells. The fibres 
^vhich extend from them often branch dichotomoDsly besides possessing many small 
lateral off sets. 

The Sylvian aqneduct expands snddenly immediately after passing beneath 
the posterior commissure into a comparatively large, laterally nompressed cavity, 
termed tbe third v«jitricl« (fig. 73). This, which is deeper in front than behind, 
passes at ito anterior and lower extremity to.a cooical termiuatioD which lies over the 
Fig. 73.— ViBW VROH iBovK or trie 


The bnin hu been aliced horiiontally 
immedialelj below tbo corpus callosum, 
Mid tbe famli and Telum iaterpositum 
hare been removed. 

TAti, tkJamuB opticiu ; Ti, ita ante- 
riOTtubercle; Pr, jiiiNinai ; C'oni, middle 
comiDiaBure etretching between tbe two 

optic tbaiami acnwt tbe middle of the , 

third ventricle ; (./, columneof the famix; 
(7n, pineal gUnd projecting downwai-di 
KDci backwB,rils betvoen the superior cor- 
pora qnadrigemina ; Ht, atria lerminnlis ; 
C», Dudena caudatus of the corpus atriit' 
turn J Vit, Tentricle of tbe septum luci- 
daoi ; C^, section of the genu of tbe 
corpUB calloaum ; Fen, comoiencemeDt of 
the piDcal atria or peduncle, T/o ; Ccp, 
poiterior cammissnre. 

optic commissure {optic recess). 
Below and behind this is a conical 
depreaaion, the infundibulum, 
leading towards the^wVutVary body 
(hypophysis cerebri). At the 
posterior extremity, immediately 
above the entrance of the aque- 
duct, and separated from it by 
the posterior commissure, is an- 
other smaller depression {pineal 
recess) (fig. 90, p. 126) extend- 
ing into the stalk of the pineal 
gland or conarium (fig. 73, Cn), 
which here projects backwards 
over the mid- brain. Another 
depression extends backwards 

over the pineal stalk ; this is termed the suprapineal recess (fig, 90). The 
ventricle is bounded hiterally by the optic ihalami (fig. 73, Tho), which come 
almost in contact with one another in the median plane ; and a little in advance 
of tlie middle of the ventricle, are actually united by a connecting ba-id of grey 
matter of variable extent, termed the middle or sojl commissure (fig. 73, Com. ; 
fig. 83, m.c.). This is sometimes double and occasionally wanting : it is liable 
to be torn across in removing the brain. The lateral walls of the cavity are 
slightly convex, and each is marked towards the anterior end by a white curved 
band, with ita convexity forwards, which becomes more prominent as it passes 
upwards towards the roof. These bauds are named the anterior pillars or columns 
of the fomic (fig, 73, Cf). Immediately behind the most prominent part of 
each of these, between it and the anterior part of the thalamus, is an aperture 
{foramen of Monro) leading into the ventricle of the hemisphere (lateral ventricle.) 


All along the upper curved margin of the lateral wall, from the pillar of the fornix 
to the pineal gland, runs a white stria, known as the atria pinealis, stria medidlarisy 
or iienia fornicis (fig. 73, Tfo), The floor of the ventricle is formed posteriorly by 
the tegmenta of the crura cerebri, and where the crura diverge from one another by 
the following parts, which have been already mentioned as seen at the base of the 
cerebrum ; viz., commencing from behind, the grey matter of the posterior perforated 
space, the corpora albicantia, sen mamillaria, the tuber cinereum and infundibnlum ; 
the lamina ciner.ea serves to close the ventricle in front. The roof of the cavity is 
limited before and behind by two commissures, named from their position, anterior 
and posterior. Of these the anterior will be described with the cerebral hemispheres. 

The third ventricle is lined, like the other cavities already described, by ciliated 
epithelium, which is thin and flattened over the roof, i.e., lining the velum and 
choroid plexuses, but longer and more columnar at the bottom and sides. The 
floor, which is narrow, is formed, underneath the epithelium, of grey matter con- 
tinuous with that of the Sylvian aqueduct, and this central grey matter extends a 
short distance upwards on the wall of the thalamus. The central grey substance 
rests behind upon the still conjoined part of the tegmenta ; but anteriorly, after 
these have diverged, it comes to the surface at the base of the brain as. the posterior 
perforated lamina and the tuber cinereum. The lateral walls of the ventricle have 
but a thin covering of neuroglia (ependyma) underneath the lining epithelium ; so 
that the white covering (stratum zonale) of the thalami comes to view through it. 

The epithelial covering of the roof of the ventricle is not free but covers the 
under surface of the median portion of an expansion of pia mater named the velum 
interpositum, which overlies the third ventricle as well as the larger part of the optic 
thalami. The epithelium follows all the inequalities of two fringed vascular tracts 
(choroid plexuses of the third ventricle) which project downward from the mem- 
brane, and it becomes torn away when the pia mater is removed. At the pineal stria 
(Gg. 73, T/o) on either side it is continuous with the epithelium covering the lateral 
wall. This stria therefore represents the limit of the third ventricle so far as the 
lateral boundaries of the roof are concerned : the upper surface of each optic thala- 
mus is excluded from this cavity. 

The central grey matter of the aqueduct (fig. 76, c. gr.) is a layer 2 to 3 milli- 
meters thick which surrounds the aqueduct, and is prolonged from the grey matter 
of the fourth ventricle. It contains, scattered through its substance, nerve-cells of 
varying size, the largest being prolonged upwards from the locus coeruleus of the 
fourth ventricle ; the cells are very numerous and small at the dorsal side of the 
aqueduct. In addition to these scattered cells the grey matter of the aqueduct 
contains certain more defined groups or columns of cells which are connected with 
the roots of the third and fourth, and of the fifth cranial nerves. Amongst the 
cells there is a network of fine medullated nerve fibres, whilst near the aqueduct 
and immediately under the ependymal layer many fine longitudinal fibres are seen. 

The nuclei of the third and fourth nerves (fig. 7G, nJII,, IV. extend on 
either side along almost the whole length of the ventral part of the aqueduct, 
close to the middle line, the nuclei of the two sides being only separated from one 
another by the raphe ; at one part they even meet across this (fig. 78, nJII), 
The cells of these nuclei are large and irregular in shape, and of a yellowidi 
colour. The nucleus from which the root-bundles of the fourth nerve spring 
does not begin to show itself until the level of the upper part of the inferior 
corpora quadrigemina, and it here lies just below and rather to the side of that 
from which the bundles of the third originate. From here the bundles of the fourth 
pass obliquely downwards towards the pons, and just before reaching this the nerve 
turns sharply dorsal-wards, and passes into the superior medullary velum, in which 
it crosses horizontally, decussating with that of the opposite side (fig. 72). 


The nneleuB from which the third nerre takes origin extenda upwards uoderneath 
the superior corpora quadrigemioa, ventral to the Sylvian aqueduct, and even extends 
into a correaponding situation in the posterior part of the third ventricle. The 
anterior (superior) part is composed of smaller cells than the other portion ; it 
extends forwards into the wall of the third ventricle, and from the experiments of 
Hensen and Voeickers and the observations of Starr, it appears to be subdivided 
into two portions, of which that which is the more mesial, and lies just above the 
corpora mamilJaria, is connected with the fibres of the third nerve to the ciliary 
muscle, whilst that which is the more lateral is connected with the fibres concerned 
with the contraction of the sphincter pupille. The main part of the oculomotor 
nucleus is formed by large cells, which tend to be grouped (see diagram, fig. 74). 
Thus, there are two distinct groups on each side which are dorso-lateral (dorsal 
nuclei), and two which are ventro-mesial (ventral nwlei). These four nuclei are 
grouped around a central nueUm which lies in the middle line. Besides these, 
there is an elongated nucleus of small cells which inferiorjj (caudalwarda) 
lies in close contact with the cen- 
tral nucleus but superiorly curves 
ontwards. This is known as the 
nucleus of Edin^er and Westphal, 
but it is uncertain whether it gives 
origin to any fibres of the third 
nerve. It has not been certainly 
ascertained from which of the seve- 
ral groups the fibres to i)articular 
muscles moving the globe of che eye 
proceed. From the several groups 
of cells which constitute the oculo- 
motor nucleus the fibres of the third 
nerve pass with a curved course 
through the tegmentum, to emerge 
at the inner margin of the crusta of 
the same side ; but the fibres from 
the posterior of the dorsal groups 
andei^o decussation. These fibres 
are believed to pass to the internal 
rectus of the opposite side. 

In a caae reoorded by Kahler and Fig. 74.— Diioiuic o» thv obocm Of cilu foBMUto 
Pick, in which there waa patalTBie of '^^ huclbi of th» tbibh ird ronRXH kietis. 

the levator palpebrffi, the reotns enperior (Perlia.) 

and the obliquos inferior, a lesion wsa 

fonnd involving the posteni-liiteral bundleof the nerve-rooU. The obBerrationB of Sterr point 
to these three mnBcIes beini; innervated from the doraal (dorso-latersJ) groupti, xaA the rectDB 
intemuB and rectus inferior from the ventml (ventro-meaial) groups, in the older here given 
(from above down). 

It has been shown by Duval and Laborde that the third nerve receives fibres 
from the mesial part of the posterior longitudinal bundle of the opposite side 
(possibly some fibres also pass to it from the posterior longitudinal bundle of the same 
aide). These fibres are derived mainly from the nucleaa of the sixth nerve, and pass 
out along with the fibres of the third nciTe to the internal rectus, so that the nucleus 
of the sixth thus supplies both the external rectus of the same side entirely, and the 
internal rectus of the opposite side partially (fibres derived from the nucleus of the 
third also going to the internal rectus). These are, it may be noted, the muscles 
which are brought together into action in conjugate deviation of the eyes to either 



Bide, and the cases which are sometimes met with of conjugate paralysis involving 
the internal rectus of one side, and the external rectns of the other side, which 
are accompanied by atrophy of the nucleus of the sixth, are thus accounted for. 

The prolongation of the upper nucleus of the fifth nerve consists of a small 
number of large globose cells (figs. 75, 76, d,V), which lie at the extreme lateral 
margin of the grey matter of the aqueduct close to the bundles of the descending 
root of the fifth nerve, towards which their axis-cylinder processes are directed. This 
nucleus and root gradually become smaller, and disappear before the superior end of 
the mesencephalon is reached. 

The crura cerebri (fig. 32, F) emerge from the upper border of the pons and 
diverge from one another, leaving between them the posterior perforated space and 
the corpora mamillaria and disappearing in the cerebral hemispheres under the 
Optic tract. The triangular interval seen at the base of the brain to be enclosed 
between the diverging crura has been termed irigonum interpedunculare by 
Schwalbe. Near the point of the angle of divergence the roots of the third nerve 
issue in several bundles from a groove along their inner side (fig. 82, ///.) ; and 
this groove serves to indicate the separation between the more prominent ventral 
part of the peduncle ( pes a. basis s. crusta pedunculi, fig. 75, cr.) and the dorsal 
and larger part {tegmmtumy i.) which is in great measure concealed from view by 

Fig. 75. — Outline of two sections across 
THE mesencephalon. Natuial size. 
(E. A. S.) 

A, through the inferior pair of the corpora 
quadrigemina : b, through the superior pair. 

cr, crusta ; «.n., substantia nigra ; t, teg- 
mentum ; 6, Sylvian aqueduct with the cen- 
tral grey matter ; c.q., grey matter of quad- 
rigeminal bodies ; l.r/., lateral groove ; jp.Z., 
posterior longitudinal bundle ; d. V, descend- 
ing root of fifth nerve; i.c.p.^ superior cerebellar peduncle ; /, fillet. The dotted circle in b indicates 
the tegmental nucleus. 

the pes when viewed from below and in front. A section into the crus cerebri 
shows the two parts of which it is composed to be separated from one another by a 
tract of dark coloured grey substance known as the substantia nigra (fig. 75, sn), 
which comes to the surface on the inner side at the groove above mentioned from 
which the third nerve issues (sulcus oculomotorii), and on the outer side also along 
a grooved line — the sulcus lateralis (fig. 75, Lg,). 

Of the two main parts of each peduncle the crusta {cr) is formed almost entirely 
of lamellated bundles of longitudinal fibres, some of which are continuous with the 
pyramid-fibres of the medulla oblongata and pons, whilst others are superadded ; and 
the tegmentum is a continuation of the formatio reticularis of those parts, with the 
addition of much grey matter and white fibres, amongst the latter being those of 
the superior peduncle of the cerebellum. The two ventral portions (crustae or pedes) 
are entirely distinct from one another (as shown in the accompanying sections, 
fig, 75), and each is marked off externally from the tegmentum of the same side by 
the grooves just mentioned ; but the two tegmenta are united in the median plane 
by a prolongation of the raphe, and extend dorsally at the sides of the aqueduct to 
become continuous with the bases of the corpora quadrigemina. 

Cnuita. — The crusta is semilunar in section, the substantia nigra projecting 
into it with an irregular convex border. It is made up of longitudinal white fibres 
which become arranged in the higher parts of the mid-brain into fiattened bundles, 
with their edges dorsal and ventral, separated from one another by processes of pia 
mater. The main part is a direct prolongation of the longitudinal bundles of the 
pons and passes superiorly towards the internal capsule of the cerebral hemisphere. 


Close to the substantia nigra, the bundles of white fibres are smaller and some- 
what separated by projections of the grey matter extending between them. They 
have received the name of stratum intermedium. These are usually stated to have a 
different origin and destination from the other fibres of the crasta, passing, accord- 
ing to Meynert, between the lenticalar nucleus of the corpus striatum (see p. 181), 
and the substantia nigra and reticular formation of the bulb and pons. It is 
doubtful, however, if this is true for any of these fibres, and is certainly not the 
case with the majority, for (in monkeys) after a lesion of the Rolandic region, most 
if not all the fibres of the stratum intermedium undergo degeneration along with the 
fibres of the pyramidal tract, to which, therefore, they must be regarded as belonging. 
The pyramidal tract of the mesencephalon, or continuation of the pyramid- 
bundles of the pons, occupies about the middle third of the crusta. Superiorly 
its fibres pass through the middle part of the internal capsule to the fronto-parietal 
or Rolandic region of the hemisphere. By far the majority arise from the cortical 
cells, but a few have their cell-origin in the cord or bulb, and degenerate after 
lesions of these parts. 

It is remarkable that whereas in the lower part of its course (spinal cord and 
bulb) the fibres of the pyramidal tract acquire a medullary sheath later than the 
other fibres of the white columns, in the upper part (crus cerebri and cerebrum) it is 
acquired earlier than in the other fibres. 

The outer or lateral third of the crusta is formed of fibres which are traceable 
downwards to the lateral longitudinal bundles of the pons, and upwards to the 
posterior part of the internal capsule, but their origin and destination have not yet 
been satisfactorily made out. They are probably connected superiorly with the 
occipito-temporal regions of the cerebral cortex, and according to Flechsig they arise 
below from the cells of the nuclei pontis. 

The mesially situated bundles of the crusta are also distinct from the pyramidal 
tract proper (Flechsig), being developed at a later period. They are perhaps 
connected through the anterior part of the internal capsule with the prefrontal 
region of the hemisphere. Finally, one well-marked bundle in the crusta is con- 
nected with the fillet {mesial flllet, pp. 66, 67, and 103). This bundle is at the 
lateral border of the pyramidal tract in the upper part of the crusta, but lower down 
crosses obliquely over or between the fibres of that tract to attain the mesial border 
of the crusta, whence it is ti-aceable to the fillet. It contains, according to Spitzka, 
the afferent cerebral tracts of the cranial nerves. Traced upwards it is lost in the 
subthalamic region. 

Lastly the crusta includes some fibres derived originally from the cerebellum and 
joining the pyramidal tract in its passage through the pons, such fibres being 
scattered amongst the fibres of the other tracts. 

The substantia nigra is a mass of grey matter which is characterised by the 
presence of a number of very darkly pigmented irregular nerve-cells, which give the 
substance in which they are scattered the appearance from which it derives its name. 
It forms a layer whicli separates the crusta from the tegmentum. It is thicker 
near the mesial border of the peduncle than laterally, where the tract of the fillet 
may be but incompletely separated by it from the longitudinal bundles of the crusta 
It commences at the upper margin of the pons, and can be traced as far forwards as 
the posterior border of the corpora albicantia. At the origin of the third nerve it is 
traversed in its mesial part by some of the issuing fibres of the nerve-root. The 
grey matter of the substantia nigra projects here and there between the adjacent 
bundles of the crusta ; one considerable projection in particular in the lower part 
of the mesencephalon serving to mark off the mesial portion of the crosta from the 
rest. The cells in this projection are much smaller, and relatively more numerous 
than in the rest of the substantia nigra. 


The tsgrneutiun, like the fonnatio reticularis of the bulb and poDB, of which 
it ia the prolongation upwards, is composed of Bmall longitudinal bundles of white 
fibres, separated by transversely coursing or arched fibres, ti^ether with a con- 
siderable amount of grey matter containing scattered nerve-cells, 

Iq addition to these diffused bundles of longitndinal fibres there are others 
which are collected into more defined tracts. One such tract constitutes the 
posterior or domal loi^tnduial bundle, which ia seen in all sections of this 
part of the brain as a pyriform area of transversely cut fibres which lies on each side 
of the middle line between the grey matter underlying the aqueduct, and the 
fonnatio reticularis (fig. 7G,p.!.b.). The fibres which constitute this bundle below 


MtONTFllD ABOUT 3J DiAVKTiRS. (E. A. S.) Prom ft Pbotogntpfa. 

gr,, dorsal qnadrigemiiuil gnoie (salcne loDgitiidiiiali»] ; r.j.p., corpns quadrigcmmnm postcriuE; 
llr.l., etrtktnm Umnisci ;, central gre; matter ; tt.lll, IV, oculo-motor DucleuB : d. V, descendbg 
root of fifth nerre ; p.l.b,, posterior longicuilinal bundle ; f-r.U, forrnatio reticularis tegmenti ; d, d", 
decoraatiDg fibm of tegmeatum ; i.c.p., decDButiog fibres of euperior cerebellar peduncles ; /, upper 
fillet ; /', lower or laieml fillet ; p.p., pes peduncnli ; ».n., substantia nigra ; ff.i.p., interpeduncnlar 
grej matter ; Sy, Sjlvisn aqueduct. 

have already been noticed (see p. 65 and figs. 53, 54) ; traced upwards its fibres 
become related to the nuclei of the third and fourth nerves, and mostly pass out with 
the roots of these nerves. The posterior longitudinal bundle is composed exclusively 
of large nerve-fibres, which acquire their myelin at an early stage, in fact, as soon 
as the root* of the nerves themselves. Although it* fibres are large, it gives off 
principally fine nerve-fibres (Koppen). If this is the case they are probably 
collaterals. It appears to be developed in nearly all vertebrates, and in some is 
better marked than in mammals ; e.g., in the lizard it can be traced right down the 
cord dorsal to the anterior or ventral commissure. Although mainly related to the 


sixth, fourth and third nerve-roots, fibres also pass from it to the auditory nucleus, 
and others to the cerebellum. After giving olf fibres to the root of the third nerve the 
posterior longitudinal bundle is continued into the posterior commissure (see p. 109), 
and partly upwards into the subthalamic region (? to the substantia interansalis, see 
p. 112). The posterior longitudinal bundles come close together at the raphe, and 
fibres pass from one to the other. These are probably the fibres which effect a crossed 
connection between the abducens nucleus of the one side and the fibres passing to 
the internal rectus by the third nerve of the other side (see pp. 03 and 99). Perhaps, 
also, a connection is established through the posterior longitudinal bundle between 
the facial and the oculomotor nucleus (Mendel). The posterior longitudinal bundle 
is very small in the mole (Forel), large in reptiles and amphibia (Spitzka). 

Brachiam coi^unctivum ; saperior cerebellar peduncle. — ^Another tract 
of longitudinal and decussating fibres is derived from the superior peduncle of 
the cerebellum, which we have already traced as it passes forwards over the 
superior end of the fourth ventricle. Reaching the sides of the aqueduct as a 
well-marked bundle, of semilunar shape in section (fig. 72, s.c,p\ it gradually takes 
a more ventral position as it is traced upwards in che mesencephalon, and its 
fibres soon begin to pass across the raphe, decussating with those of the other side 
(fig. 75 A, and fig. 76, sx,p,), the decussation extending as far upwards as the superior 
pair of corpora quadrigemina. Having thus crossed to the opposite side the tract 
in question pursues its course longitudinally upwards, appearing at fi i*st as a white 
bundle, but higher up enclosing in its pas<<age a tract of grey matter with numerous 
large pigmented cells, known as the nucleus of the tegmentum or red nucleus (fig. 
75, B, and fig. 78, r.n.), and probably receiving an accession of fibres from these cells. 
Above, the tract passes into the ventral part of the optic thalamus. Some fibres 
do not cross, but enter the red nucleus of the same side. 

Between the two red nuclei a small white bundle {MeynerCs bundle) passes 
backwards on either side of the raph6 from the ganglion of the habenula near the 
roof of the third ventricle to a small mass of grey matter which lies between the 
crura {ganglion interpeduncvlare^ fig. 76, gA.p,), 

Tract cf the fillet. — The fillet, which, in sections across the upper part of the 
pons, forms a considerable flattened bundle of longitudinal fibres at the ventral 
border of the formatio reticularis, is traceable upwards into the ventral part of the 
tegmentum. Soon, however, the large laterally situated part of this tract is seen to 
pass obliquely outwards and emerge at the side of the crus cerebri, curving obliquely 
over the outer side of the prolongation of the cerebellar peduncle {^g. 75, a, /), 
and tending for the most part towards the inferior corpora quadrigemina. It is seen 
on the surface as a band of obliquely curved fibres, occupying a triangular area at 
the side of the tegmentum (fig. 76,/'), and it was to this band that the name of 
fillet was originally applied by Reil. It is now known as the lotver or lateral fillet. 
It is reinforced by fibres from the superior medullary velum which also curve round 
the superior cerebellar peduncle, and which are probably derived from the antero- 
lateral ascending tract of the cord, for they undergo degeneration ader section of 
the cord (see below). The fillet is covered externally by a thin layer of grey matter 
containing nerve-cells. 

But all the fibres of the tract of the fillet do not take the course above indicated. 
Those nearest the middle line {mesial fillet) separate themselves from the rest, and 
pass at the lower part of the mesencephalon into the crusta (see p. 101), where they 
form a mesial bundle (Wernicke), which is traceable up into the subthalamic region, 
where it joins the ansa lenticularis. Those next in order {middle portion) are for 
the most part, according to Forel, continued upwards in the formatio reticularis 
of the tegmentum, but many of the fibres become lost amongst its cells, and 
are not traceable further as a distinct tract. According to Edinger, they have a cell- 


station in a special group of nerve-cells (upper nucleus of the fillet) at the level of the 
inferior corpora quadrigemina. Some of the lateral fibres of this middle portico, 
however, pass to the upper corpora quadrigemina {upper fillet), and even extend 
beyond the superior quadrigeminal region to the subthalamic region (Flechsig), 
eventually reaching the parieto-occipital part of the cerebral hemispheres by the 
posterior part of the internal capsule (v. Gudden). Both the upper and lower fillet 
receive fibres from the antero-lateral columns of the spinal cord, for after hemisection 
of the cord degenerated fibres are seen on the same side, both in the lateral fillet of the 
mesencephalon, where they are mingled with the mass of undegenerated fibres which 
have been derived from the nucleus gracilis and nucleus cuneatus (see p. 53 and 
below), and in the bundle of the upper fillet, which enters the superior corpora quadri- 
gemina J a few degenerated fibres are also seen in corresponding positions on the oppo- 
site side. Traced downwards the fibres of the lower fillet pass, as we have seen, a tew 
by means of the trapezium towards the auditory nucleus of the opposite side, a few 
to the antero-lateral column of the medulla oblongata and cord (antero-lateral 
ascending tract), but most are traceable to the anterior column of the medulla 
oblongata dorsal to the pyramids, and passing across the raphe, proceed as internal 
arched fibres to the nuclei of the posterior columns, from the cells of which they in 
all probability arise. 

To sum up : — The fillet as a whole is composed of ascending fibres, most of which 
are derived from the nuclei of the opposite posterior columns of the medalia 
oblongata, but a few from other sources. The fibres of the antero-lateral ascending 
tract which enter the fillet may, according to Edinger, be derived from cells of the 
opposite posterior horn of the spinal cord ; if so, all the fillet-fibres may be regarded 
as having crossed over from the opposite side, some in the cord, others at the 
superior or sensory decussation in the medulla oblongata. The fact that they are 
thus derived is however by no means certain. Superiorly the fillet may be described 
as being prolonged upwards above the pons in three parts, of which one— the lower 
fillet — goes to the inferior of the corpora quadrigemina of the same side, a second — 
upper fillet — to the superior corpora quadrigemina and occipital region of the 
cerebral hemisphere, and a third, mesial fillet, to the base of the cerebrum through 
the crusta. 


As before stated the Sylvian aqueduct is covered on its dorsal aspect by the 
quadrigeminal lamina, bearing the bodies of the same name. The median part of 
the lamina is marked by a comparatively wide groove {sulcus longitudinalis^ 8. 
8agittdlis)y shallower inferiorly, which serves to separate the corpora quadrigemina 
of opposite sides (fig. 77). This grooved surface, which is raised above the level of 
the upper medullary velum, is connected with the velum by a small median strand 
of longitudinal fibres termed \hQ frcejiulum veli (fig. llyfr). In front of the upper 
(anterior) pair of corpora quadrigemina the groove is interrupted by a transverse 
white prominence — the posterior commissure ; but both this and the upper end of 
the median groove are in the natural condition concealed by the pineal body (p), 
which projects backwards and downwards from the posterior wall of the thinl 
ventricle and rests between the upper pair of quadrigeminal bodies. A well-marked 
narrow transverse groove (sulcus transversus) which conmiences a short distance 
from the middle line, and is curved round the lower border of the upper tubercle, 
separates this from the lower tubercle of the same side. 

The corpora quadrigemina are two pairs of rounded eminences which are 
mainly composed of grey matter, although covered externally by and containing in 
their mterior many white fibres. The upper or anterior tubercles (fig. 77, c.q.8.) 


are broader and longer and also darker in colonr, but slightly less prominent than 
the lower or posterior {c.g.iy. Latemllj the corpora quadrigemina are not bonnded 
by a distinct groove, but each appears to be prolonged obliqnely upwards and forwards 
into a proroineot white tract, known as the hrachium of the corresponding tubercle. 
The lower (posterior) brachium (fig. 77, br.i.) loses itself underneath an oval 
prominence which is seen at the side of the npper end of the cms cerebri, and is 
termed the inner geniculate body (fig. 77, cg.i. ; fig. 78, cg.m.). The upper (anterior) 
brachium passes between the same geniculate body, and the prominent posterior 
extremity of the optic thalamus into the external geniculate body (fig, 78, cg.l.) and 
the (qjtic tract, of which it may be regarded as the main prolongation (see also fig. 8G, 
p. 117). The continuity is much better seen eitemallyin some animals than in man. 
The connection of the superior quadrigeminal bodies with the optic tract and the 
sense of sight is far more intimate than that of the inferior. For if in a young 
animal the eye on the one side be extirpated, the operation is fouad to he followed 

Fig. 77-— VlBW 0» TBI HELUILI, F0»9. AND 


Tbc cerebellum, the inferior medultai? Telom, 
and the right bidf of the superior medallatj 
velum, baTe been cut awajr, so as to displik; the 
fourth Tentricle. 

e.q.i, c.q.i, Boperior and inferior qnadri- 
geminal bodies of the left side ; tbo pineal 
gland, p, is seen projecting backirards betveea 
the KUperior bodies, and the fnsaulum. fr, 
passes up from the Bni>erior medullary velum, 
s^ta.r, to the interval between the posterior 
quadrigeminal bodies ; lA, right tbalamun opti- 
cus; Ar.j, b^a(^hiumof the inferior quadrigeminal ' 
boilj psniiig andemealli the inner geniculate 
I»>*'Tt t.g.i. ; /, auperliciBl stratum of fibres of 
tbe fillet, covering the tegmentum of the crus 
cerebri ; c, cruata of the cnn cerebri, separated 
from the tegmentum bj tbe lateral groove, l.;/. ; 
P, upptr part of tbe pons ; III, IV, &c,, the 
corresponding cranial nerves. The rest of this 
fignre vill be found deecribeJ at p. IS. 

after some time by atrophy of the 
superior quadrigeminal body aud of its 
brachium, whereas the inferior quadri* 
geminal body and brachium is un- 
altered (Gudden). Moreover, iu the 
moie the inferior quadrigeminal body 
is Well developed, whereas the superior 
IB atrophied. 

The lower or poBt«rior qnadri- 
geuinol bodies are composed almost 

entirely of grey substance (the so-called nvfleus of these bodies (fig. 76, c.g.p.) which 
is separated by a thin layer of the fillet from the central grey matter of the aqueduct 
and contains numerous small and some larger nerve-ceUs. The connections of these 
have not yet been satisfactorily worked out, but they are believed to be closely 
related to the termination of the fibres of the lower fillet. The nuclei are united 
across the middle line by a commisanral portion of grey matter which is bounded 
euperficially and deeply by transverse white fibres derived fcom the fillet, 

' The term win is often applied to the eoperior or anterior corpora qoadrigemina, and tiiUt to the 
inferior or posterior. Theee names weiB used b; Vesallus, but are somewhat misleading, and have fallen 
into disnae. 


The Biiper6cial fibres are continuous laberally and above with the fibres of the 
bmchinm of the inferior qnadrigeminal body, and laterally and below with thoee of 
the lower fillet. On the other hand, if the fibres of the lower fillet are traced down- 
wards, they are partly found as we have already seen (p. 101) to be continuous with 
fibres of the trapezium ; which again is connected with the principal nucleos of the 
auditory nerve (cochlear division) of the opposite side (Flechsig). This would 
appear to indicate a close connection between these posterior or inferior quadrigemi- 
nal bodies and the auditory nerve, and in conformity with this view it is noticeable 
that it is only those animals (mammals) which have a well-developed spirally wound 
cochlea that show the inferior corpora quadrigemina as distinct prominences. In 
nearly all vertebrates below mammals there ate merely corpora bigemina, and these 
seem mainly to represent the anterior pair of the quadrigemina of mammals. As 

(E. A. S.J 

Sy., aqnedurtus Sjl/ii ; e.p., oommiaaurtt posterior ; gl.pi., glandula piaealb ; c.q.a., grey matUr of 
one of tbe aaperior corpora quadrigentma ; cff.m,, corpus geDiculatum mesiale ; cg.l., corpaa genicD- 
latum Uterale ; tr. opt,, tractus opticus ; P-p-, pss pednnculi ; p.i.b., poslerioj- longitndinat bundte ; 
ji., appar fillel ; r.n., rtd nucleus ; n.III, nucleus of third nei-ve ; ///, isaving fibres of third nerve ; 
l.p.p., loous perfotfttufl posticus. 

already mentioned, this anterior pair is chiefly connected with the optic nerves and 
therefore with the visual sense. 

The upper or BAterior quadrigemiiuil bodiss of mau have been carefully 
investigated by Tartuferi. Moat externally or uppermost is a thin layer of superficial 
neuroglia, containing no nerve-cells or fibres, but only fine stellate glia-cells and 
the ends of glia-fibres which radiate from the central canal (aqueduct) towards the 
periphery. Excluding this neuroglia-layer, and also the central grey matter around 
(he Sylvian aqueduct, Tartuferi distinguishes four strata in vertical sections. 


1. Stratum zonaU; superficial white layer, — This is a relatively thin stratum of 
transversely conrsing fine nerve-fibres, which are derived through the superior 
brachium from the optic tract and retina.^ Many of them dip down and lose 
themselves in the next layer, but some appear to be continued towards the middle 
line and to decussate with others irom the same stratum of the opposite side. 

2. Stratum cinereum ; gret/ cap. — A layer of grey matter, semilunar in section, 
being of considerable thickness opposite the most prominent part of the tubercle, 
but thinning off at its margins. Its nerve-cells are numerous but vary in size, the 
smaller ones being near the stratum zonale, the larger in the deeper part of the 
layer. They mostly send their dendrites or protoplasmic processes outwards, 
i.«., towards the stratum zonale, while their nerve-processes (axis-cylinder processes) 
are directed inwards towards the deeper layers. 

8. Stratum albo-cinereum superius ; upper grey-white layer ; stratum opticum. — 
The grey matter of this layer is largely interrupted by nerve-fibres, which are 
continued like those of the stratum zonale from the optic tract, which enters by the 
superior brachium at the antero-lateral aspect. The fibres differ in calibre in the 
different parts of the layer, and it may be subdivided accordingly into (a) a medio- 
dorsal zone of coarse meduUated fibres, (/3) an intermediate zone of fine medullated 
fibres, and (y) a central zone containing much grey matter interspersed with bundles 
of white fibres. 

These are described by Granser as three distinct layers, and termed the third, or superficial 
medullated layer, the fourth, or middle medullated, and the fifth, or middle grey layer ; while 
the fourth layer of Tartuferi, immediately to be mentioned, becomes the sixth and seventh of 

The whole stratum is richly beset with large nerve-cells, which send their axis- 
cylinder processes mostly into the next or fourth stratum. Of the nerve-fibres, those 
of the intermediate zone (/3) are retinal fibres according to Tartuferi ; those of the 
central zone (y) are probably derived from the corona radiata of the occipital region 
of the brain, whilst the coarse fibres of the medio-dorsal zone are perhaps derived 
from the opposite side. 

4. Stratum dllo-cinereum inferius: deep grey-white layer: stratum lemnisci, — 
This, although composed of grey matter, is also traversed by many nerve-fibres which 
appear to be connected with the upper fillet, and probably end in the layer. Some 
of the fibres, however, are derived from the large cells of the fourth layer, and others 
from the nerve-cells of this stratum itself (which contains many cells of large size). 
It is possible that some fibres are derived (over the aqueduct) from the fillet of 
the opposite side. 

Ganser subdivides this layer into two, which he terms respectively the deep white (sixth), 
and the deep grey (seventh) layera. 

Structure of the optic lobes of birds. — The relations of the cells and fibres have not 
been very satisfactorily made out in the corpora quadri^emina of mammals, but in the optic 
lobes of the bird, which correspond, as we have seen, to the anterior or superior quadrigeminal 
bodies of the mammal, these relations have recently been considerably elucidated by the 
investigations of Eam6n y Cajal. 

All who have specially worked at this subject distinguish more strata in the optic lobes of 
birds than in the corresponding bodies of mammals. Thus Bellonci makes the number of 
layers (exclusive of the central grey matter of the aqueduct) nine, Stieda, twelve, whilst 
Cajal distinguishes as many as fourteen strata. Of these the most superficial (1.) is a layer 
of thick medullated fibres coming directly through the optic tract and chiasma from the 
retina of the opposite side. (In birds all the optic nerve-fibres cross at the chiasma.) They 
pass in from the side (so that they are cut across in a sagittal section, fig. 79), and after a 
variable course turn downwards into the deeper layers, where they end at four different levels 
(as far as the seventh layer) in non-medullated terminal arborisations. Of these terminal 

' Monakow states that in the dog the anterior brachinm contains some fibres from the occipital cortex. 


ramiaefttionB, that in tie eerenth layer ie flattened horizontally, the others are i 
yertioaJiy (fig, 80). Some of these terminal arborlBationa end in a special circumgcribed part 
of the lobe, which la known mihe gaiigUt'Hii/ tlte roof. ThisoontaioH a large nomber of nerre- 
cellB, the protoplaamic processeB of which interlace with the optic arborieationB, whilst theii 
nerre-fibre prooeiwes are directed towards the deeper layers of the lol)e. All the layers below 
the first contain netve-celis, as well as nerre-fibres, bot the seventh is mainly composed of the 
expanded ramlGcstions of the optio fibres just men- 
tioned, and of similar expanaiona of the superficially 
1 directed nerve-fibre processes of cells from the tenth 

layer (fig. 7%j,j). The cells vary in siie and shape 
in the different layers, bnt on the whole they are 
smallest nearer the surface and largest in the deepsr 
layers (tenth to thirteenth). With the exception 
^ of the oetU of the tenth layer just mentioned, the 

cells send their axis-cylinder procesaea downwards t« 
5 peas away as nerve-fibres of the fourteenth layer. 

which is chiefly formed of lartre medullatcd nerre- 
fibres, althoufih some nerve-cell* are even here int«r- 
7 spersed. Bnt some of t<he smaller cells of the more 

superficial layers (fig. 79, d) belong to Ool^'s 
i second type of nerve-ceU, i^., their azis-Cflindar 

processes do not pass into nerve-Bbres, but break up 
into a terminal arborisition a short distance from the 
S cell, and interlace amongst the cells of some of 

the other layers. The third, fifth, seventh, and ninth 
layers oil have relatively few oells and a molecular 
aspect, due apparently to the fine arborisations of the 
^^ nerve-fibre or aiis-oylinder processes which they con- 

tain. The protoplasmic processes of the cells are, some 



(R. y Cajd). 
a, optic fibres cot across ; b, stellate cell aC second layer ; c, fasiform cell of thjnl layer ; d, cell 
with axis-cylinder ending in a varicuse arborisation id the eighth layer ; e, lat^ge horiiontal cell of fourth 
layer ; /,ff,lt, globular cclla o( eighth lajer ; i, ttll with descending axis-eyliailar of this layer ; j, celt 
with axis-cylinder ascending to optic Isyer ; t, collateral arborisation of tfaia axis-cylmder in the seventh 
layer : nt, large fuciform oclls with recurrent axis-cyliadeis ; n, pyramidal cell with descending mit- 
cyliniler; o, large cell of tenth layer; p,q,T, cells of Ihe lonost layers, all with aiis-cylindera directed 
towards the deep layer at nerve-tibres, i. 

Fig. 80.— Thinsvkrse section or oftio LaBR of a bibd, Ooloi's xetqod (R. y Cajal). 
The superficial part only ia represented, as far as the seventh layer. 

a, optic fibres ; b, their arhoriwition in the second layer ; e, that in the fourth Uier ; d, that in the 
fifth layer ; e, that in the seventh layer. 

of them, very long, and when coursing vertically oft«n extend as far as the layer of optic 
fibres, on the one band, and the deep me<lullary layer on the other. The axis-cylinder 
processes sometimes come off from the dendrites, sometimes from the body of the cell. Of 
the fibres which form the deepest layer, although many, as Just stated, are derived from tho 


oellt of the optic lobe, and are therefore psa^ag &\re^ by that layer (probably t<i the higher 
pttrtt of the brain, on the one band, and to the bulb and apinal cord, on the other), some have 
a oontnuy direction and are passing ialo the grey matter, where thej end in extenaiva 
ramiGcaCioiu extending as far towards the surface as the sixth layer. 

The fibrsH of the deep mednllary layer, on leaving the optic lobe, partly encircle, partly 
tsaTetee, four group* of nerve-oells, wUch are known as the aptic ijangliq. It is probable 
that these may in part represent the external or lateral genicQlate body of maminalB. The 
fibres give off collaterals, which end in ramiflcations amongst the cells of these ganglia; some 
of the fibre* appear alt^ether to terminate in this way. On the other hand, some of the 
ganglion-cells send their axis-cylinder processes to join the stream of travereing nerve- 
fibrea. It is not known what ultimately becomes of these processes, but from analogy 
with what obtains in mammals (see diagram, p. 119), it is not improbable that they may pass 
to the cortex cerebri 

The posterior oonunlsaare (fig. 73, Cop., 6g. 78, cp-'), which overliea the 
upper end of the aqueduct and appears in the posterior wall of the third ventricle, 
is generally described with that cavity. It appears, however, to be ia part a coa- 


I, aqueduct of Sjlviai ; gr, grey matter of the aqueduct ; c.q.i, qnadrigeminal eminence, consisting 
of : ', ■iratum lemnisci ; o, Btrstum opticum ; e, etiatum einereum ; Th, thalamaa (palvioar) ; c.g.t, 
e.g.t, internal and eitemal gsnienlate bodies ; ftr.j, br.i, aoperior and inferior brachia; /, npper fillet ; 
p.l, posterior longitudinal bundle ; r, raphi ; III, third nerve ; n.III, its nucleus ; l.p.p, poaterior 
perfoi-Btsd apace ; i.n, sabstantia nigra ; above thia is the tegmentum with its nucleus, the latter being 
iodiciled bj the circolar area ; cr, emsta ; II, optie tract ; M, medullar; centre of the hemisphere ; 
n.1^ nucleus csudatus ; it, stria tanmnBlii. 

tinuation of the commissnral fibres of the fillet above mentioned. Its fibres, 
according to Meynert, coming from the tegmental part of the mesencephalon, cross 
to the other side, and after passing throngh the thalamus diverge into the white 
snbalance of the cerebral hemispheres. They may in part comprise commissural 
fibres between the two thalami, and some are connected with the pineal roots. 
According to Darkscbewitsch they are divisible into two categories. Some form a 
ventral portion of the commissure, being derived from the posterior longitudinal 
bundle and the nucleus of the third nerve, and pass across to the root of the pineal 
body of the opposite side, while the rest, which form a dorsal portion of .the com- 
iniBsare, connect the deep white layers of the superior corpora qnadrigemina with 
the corona radiata of the opposite side. 

The gmionlats Twdies are intimately related to this region of the brain, the 


mesial (internal) with the inferior quadrigeminal bodies, the lateral (external) 
with the superior quadrigeminal bodies and optic tract. The two are separated by 
a part of the optic tract which aweeps round the internal geniculate body in passing 
as the superior brachium, to the grey matter of the corp. quadrig. sup. (fig. 86, p. 117). 
Both the geniculate bodies are continuous with the posterior part of the thalamus, 
lying between this and the lateral margin of the cnista. The internal geniculate 
body receives ventrally and mesially the inferior brachium, which passes forwards 
to it by the side of the tegmentum from the corp. quadrig. inf., and appears to dip 
under it. Some of the fibres of the optic tract appear to pass out of it on its latere- 
ventral aspect, but as the internal geniculate body remains unaffected when the eye 
is extirpated, and is, moreover, as well as the corp. quadrig. inf., well developed 
in the mole, it is probable that thi? connection with the optic fibres is more apparent 
than real. 

The lateral or external geniculate body is, on the other hand, intimately related 
to the optic tract and corp. quadrig. sup. as well as to the visual area of the 
cortex cerebri (occipital region). It is of a somewhat darker colour than the 
adjacent part of the thalamus with which it is intimately connected, and is formed 
of several curved layers of grey matter with white lamellae of optic nerve-fibres 
separating them (fig. 81, cgx) 

Its cells are large and pigmented, and appear chiefly to send their nerve-fibre 
processes to the cortex of the occipital region, for if this region is removed on one 
side in young animals the cells of the external geoiculate body of the same side 
undergo atrophy (Monakow.) On the other hand, if the eyes are extirpated, the 
atrophy which extends along the optic tracts involves the grey matter betweeu the 
cells, but not the cells themselves. From this it is inferred that the intercellular 
grey matter of these bodies is largely composed of ramifications (? of collaterals) 
of the retinal fibres. The same ' statements apply to the adjacent part of the 
optic thalamus (pulvinar) which appears intimately associated both in structure 
and function with the lateral geniculate bodies. 

The optic thalami (fig. 82, Thd)^ as seen from above after the removal of the 
corpus callosum, fornix, and velum interpositum, are large oval-shaped masses of grey 
substance covered dorsally by a thin stratum of white fibres. The dorsal surface is 
marked by a shallow longitudinal groove, which inclines inwards as it passes forwards, 
and terminates a short distance from the anterior extremity of the surface. This 
anterior extremity is raised into a prominence termed the anterior tubercle (fig. 
82, Ts), and together with the part of the upper surface which is placed outside 
the groove, projects into the ventricle of the corresponding cerebral hemisphere 
(fig. 88), and is covered by the lining epithelium of that cavity. This part of the 
upper surface is limited externally by a white band, the stria terminalis (Sf)y which 
separates it from the part of the corpus striatum which is seen in the lateral 
ventricle. The longitudinal groove above mentioned corresponds with the thickened 
margin of the fornix, the edge of which extends over the surface of the thalamus 
along the line of the groove. The part of the upper surface behind the groove does 
not appear in either the third or the lateral ventricle, and is therefore not covered with 
epithelium like the rest. It is limited internally by a sharp edge which separates 
it from the mesial surface and which is marked by a white stria (tssnia fomicis, fig. 
82, T/o,) leading to the pineal body. It is along this stria, which is surmounted by 
a ridge-like extension of ependymal tissue that the thin epithelium which roo& in 
the ventricle is attached laterally : this epithelium always comes away when the 
covering of the velum interpositum is removed. At the posterior and inner 
extremity of the thalamus, there is seen, as in front, a well-marked prominence 
{posterior tubercle or pulvinar (Pv) ) which projects over and pai'tially conceals the 
brachia of the corpora quadrigemina. Between the pulvinar and the peduncle of the 


piueaihodj (fiabenula) {Pen) lies a triangnkr depreaeed Bnrface, separated posteriorly 
from the mesencephalon by a transveree groove and passing mesiftlly into the atalk 
of the pineal body. This triangular surface is termed the trigonum kabetiuJa. It is 
bounded laterally by the sulcus habtnula. The mesial surface of the thalamus lies 
in the third ventricle. It is covered with epithelium and is joined with that of 
the opposite side by the middle commissure. The posterior rounded surface is 
occupied almost entirely by the pnlviuar. Below and external to this is the outer 
geniculate body, which is placed just above the inner geniculate body before mentioned 
(p. 105), the two being separated from one another by one of the roots of the optic 

Fig. 82.— View from iBovK of tub 
a (Hecle). 

The brain fais been sliced horizontalty 
immediktely below the corjiTU cnltoaqm, 
And the fornix and Telum interpoeitum 
have been removed. 

Tfto, thaUmiu opticus ; T**, its ante- 
rior tubercle i Pv, pulvionr; Com, middle 

mmminure stretching between tbe tvo I 

optic thalami acroBs Uie middle of the 
third ventricle ; Cf, columns of the tor- 
nix : Cn, pineal gland projecting down- 
wards and backwards between tbe aaperior 
corpora qaadrigemina ; Si, stria tenni- 
nalis ; Ci, nucleus caudatusof thecorpus 
striatDTn ; VU, Tentricle of the septam 
lucidnm ; CcP, section of tbe genu of the 
corpus catlosom ; Pen, pineal peduncle ; 
T/o, pineal stria ^ Cop, posterior com- 

tract (upper bracbium) (fig. 86). 
From this brachium and from 
tbe two geniculate bodies the 
optic tract curves downwards 
and forwards around the cms 

Tbe lateral and ventral sur- 
faces of the thalamus are not 
free, but are united with other 
parts of the brain. The ventral 
surface is united with a prolonga- 
tion of the tegmental part of the 
cms cerebri, and more anteriorly 
the corpus albicans and the side 
of the tuber cinereum lie below 

it. The lateral surface is covered by white substance which is formed of the fibres 
of the crusta, which here diverge into the substance of the hemisphere, and pass 
between tbe thalamus and tbe lenticular nucleus na the internal capsule. 

The tbalami optici are covered on their free surfaces (mesial and dorsal) 
(fig. 83), by a layer of white fibres, most marked upon the dorsal surface {stratum 
sonaU), and mainly running ontero-posteriorly. On their outer snr&ce, as just 
mentioned, is the white matter of the inner capsule (i. c.) formed by fibres diverging 
from the crueta into the hemispheres. Nest to the thalamus on this side is a denser 
layer of white fibres, termed the outer medullar// lamina. All along this surface 
radiating fibres pass out of the thalamus to mingle with the fibres of the inner 
capsule and to pass with these to the surface of the cerebral hemispheres. Thoae in 


front pass to the frontal lobe of the hemiBphere ; those in the middle region 
to the posterior part of the frontal and to the parietal lobe, besides some to the 
temporal lobe; those behind partly to the temporal lobe, but chiefly to the 
occipital lobe. The fibres to the occipital lobe pass oat from the lateral margin of 
the pulvinar, and have at first a curved course round the posterior horn of the 
lateral ventricle, afterwards radiating, with a generally sagittal direction, towarda 
the cortex of the occipital lobe. They are often spoken of as the optic radialions. 
These radiating fibres are continuous with others passing from the optic tract to 
the pulvinar. The lower surface of the thalamus is continuous posteriorly with the 
prolongation of the tegraentam {suithalamic Ugmental region), but in front this 


Ih, thalamoB ; a,e,i, its ulterior, ex- 

teniBl and internal nuclei respectlvelj ; 

a, its Utticeil layer; m.e., midille com- 

missare ; aboTB and below it is the cantj 

of the third ventricle ; «.c. ,eoipuH callo- 

EUiu ; /, fomii, aeparnted from the third 

veatriclo and thalaraua bj the velom 

interpoBitum. In the middle of this are 

Men the two reins of Galea and tlie 

choroii] plexuses of the third ventricle ; 

and at its edges the choroid pleiusea of 

the lateml ventricles ; (. i., tenia semi- 

circnlaris : ct. forward prolongation of the ornsta puaing laterally into the internal eapsnie, t. c. ; 

t. t. T., Bubthalamic prolongation of ihe tegmentum, consisting of (1) tha dorsal layer, (2) the tons 

incorta, and (3) the nucleus of Lnys ; >. n, , subatantja' nigm ; n. e., nncleus caudatus of the corpus 

gtriatum ; n. L, nucleus leoticularii ; e. c., eilemal capsule ; d, claustnim ; I, island of ReiL 

prolongation inclines to the outer side and becomes lost in a layer of grey matter 
which is continuous internally with the grey matter of the floor of the ventricle, 
and is seen at the base of the brain as the anterior perforated lamina. At its anterior 
end the thalamus mei^ea into a tract of fibres which stream from it through the 
internal capsule into the frontal lobe of the hemisphere (anterior stalk of thalamus). 
Other fibres curve downwards and outwards towards the white substance of the 
hemisphere forming the so-called lower stalk of t/ie thalamus (ansa peduncularis). 
Above this is another tract {ansa lenticularis), sweeping from under the thalamus 
round the mesial part of the crusta to the lenticular nucleus of the corpus striatum. 
The layer of grey substance which is interpolated between the two tracts may be 
termed substantia mteransalis ; including the two ansee it has been designated sub- 
stantia infiominata.' 

The body of the thalamus is chiefly formed of grey matter with large and small 
nerve-cells scattered in it, but their arrangement and connections with nerve-tracts 
have not been satisfactorily ascertained. Its grey matter is partially subdivided into 
two parts, the so-called inner and outer (mesial and lateral) nuclei of the thalamus 
(Burdach), by a vertical white lamina, S-shaped in section (^internal meduUary 
lamina). The lateral nucleus (e), is the larger and extends into the pulvinar ; it is 
marked externally by the radiating white lines before mentioned as passing from 
the thalamus into the inner capsule, and these confer upon its external layer some- 
what of a reticulated aspect {latticed layer, w). The mesial nucleus (t) does not 
extend into the anterior tubercle, but this part of the grey aobstoDce of the 

> The tenn " anse p£doncalaire " vas originallj used (bj Gratiolet) to incluile the whole itibalantU 


thalamus is cat off from it by another septum of white matter. The anterior 
separated part is the anterior nvcleua of the thalamus or nucleus of the anterior 
tubarde (a). It contains comparatively lai^ nerve-ccUs and from its depth a 
nnraber of fibres pass downwMiiB and converge to form a well-marked bundle 
{bundle of Vicq-d' Azi/r), which, entering Che corpas albicans, forms within that 
tubercle a sharp bend, and appears to pass upwards again in the wall of the 
ventricle as the anterior pillar of the fornix. There would seem, however, to be no 
actual continuity between the two (see pp. 139, 130). The middle commissure 
anitea the mesial nnclei across the third ventricle, and is also continuous below 
on each side with the grey matter of the cavity. It contains nerve-cells and 
transversely coursing fibres, but many of the fibres are said to loop backwards 
Dear, the median plane in place of passing across to the opposite side. 

In the trigommi habennlB is a collection of nerve-cells termed by Meynert 
the ganglion of the habenula. To it, fibres pass from the peduncle of the pineal 
body, and from it a bundle of fibres (fasciculus retrojlezus, Meynerfs bundle (fig. 


BCliTHALiHia TiaiiEKTAL Hioioir. MagnlGi^ abonC 2^ diametan. Prom n photograph (E. A. 8.). 

The Kctbo pawee nearl; horiiontatl j, soaatocutthefibreeaf the internal mpBulo Bfroati (rnnsTersely. 
It is JDBt aho7e and in front of the corpora mBmiliaria. 

t., tKnia (atlachmeDt of epithelial roof oE ventricle) ; v.JZI.. TenlriculuH tertius ; ttr.,atr'a piaealia ; 
7^, thalamuB ; n.f., meaial nucleus of thalamus; npL, optic fibres paieiag to pulvioar; z.i., zona 
incerta ; e.s,, corpus sabthalamicum ; c.i. , capsula interna ; a.l., anSEi lenticuiaria ; /., anterior pillar 
of fornix passing baclcwarde towards corpus sibicaas ; V.A,, bundle of Vicq d'Aiyr,' passins upwarili 
natl forwards from corpus albLcann into thalamus ; x,, white bundle containing a central nucleus of 
grey matter ( ? the fssciouius relrofleius of Meynert) ; ff, g", special groups of nene'Cclls, of which y" 
ia the binder end oE the ganglion iiabenulie. 

84, x) ) passes with a curved course through the tegmentum on the mesial side o 
the red nucleus towards the place where the cerebral pednncles divei^ ; where. 


aocording to Forel, ifc passes to another collection of nerye-cells, better marked in 
most animals than in man, termed the interpedunctiJar ganglion (see p. 103). 

Subthalamic tegmental region ; transitional region. — The prolongation 
of the tegmentum under the posterior part of the thalamus is divided by Porel into 
three layers, which are named respectively from above down, the stratum dorsalSy 
the zona incerta, and the corpus subihalamicmn or nucleus of Lugs (fig. 88, 1, 2, 8). 
The latter has here taken the place of the substantia nigra, lying next to the 
prolongation of the crusta, the fibres of which are seen at the side of the subtha- 
lamic tegmental region forming the internal capsule. The stratum dorsals consist 
chiefly of fine longitudinal fibres — prolonged from the posterior longitudinal bundle 
according to Meynert, or from the fibres enclosing the tegmental nucleus according 
to Forel, possibly from both sources. The red nucleus of- the tegmentum is, pro- 
longed into its posterior part, and from this a considerable number of fibres stream 
into the internal medullary lamina of the thalamus, and a well-marked bundle 
passes across the internal capsule to the lenticular nucleus. Some fibres of this 
layer, which are traceable downwards into the upper fillet (Wernicke), turn into the 
external medullary lamina of the thalamus, which lies along the mesial side of the 
internal capsule, and from here they probably diverge into the white matter of the 
hemisphere ; whilst others, coursing through the zona incerta, and crossing the 
inner capsule, join a tract (ansa lenticularis, fig. 84, aJ. and p. 112) which leads to 
the lenticular nucleus of the corpus striatum. Finally another bundle of fibres is 
said to be traceable from the mesial nucleus of the thalamus backwards through the 
subthalamic region into the dorsal part of the posterior commissure, and thus over 
the Sylvian aqueduct into the tegmentum of the opposite side. 

The zona ificerta is a reticular formation prolonged from that of the tegmentum ; 
it passes anteriorly into the substantia interansalis. 

The corpus subthalamicum, or nucleus of Lugs (figs. 83, 84, c.s.\ is a well-marked 
brown stratum of gi-ey matter containing numerous nerve-cells, and a close plexus 
of very fine medullated fibres. It is lens-shaped in section, and has an enclosing 
envelope of white substance, through which strands of fine fibres pass from the 
interior of the body mesially towards the zona incerta, and outwards and downwards 
through the internal capsule. This stratum is distinct only in the Primates. 

The pineal body or gland {coruirium, epiphgsis cerebri) (fig. 82, On, fig. 91), 
is a reddish body about the size of a small cherry-stone, and is named from its 
supposed resemblance in shape to a fir-cone. It is connected with the posterior 
part of the third ventricle, projecting backwards and downwards between the 
superior pair of corpora quadrigemina. It is attached on each side by a broad 
but' flattened stalk of white fibres (pedunculus conarii) which, is separated by the 
pineal recess of the ventricle (p. 97) into a dorsal and ventral portion. The ventral 
portion curves downwards ; it belongs to the ventral portion of the posterior 
commissure. These fibres are said to be derived from the optic tract near the 
lateral geniculate body, and to go to the oculomotor nucleus of the opposite 
side (compare p. 109). The upper portion extends on either side along the ridge- 
like junction of the upper and mesial surfaces of the thalamus as the pineal 
stria or taenia fornicis (R^. 82, T/o,), At the sides the stalk merges into the 
trigonum habenulae. The pia mater which invests the mesencephalon, covers the 
pineal gland with a special investment before being prolonged as the velum inter- 
positum over the third ventricle and thalamus ; and the gland is liable to be torn 
away in removing the pia mater. 

The pineal gland is composed of a number of hollow follicles generally spherical, 
but in some cases tubular, separated from one another by ingrowths of connective 
tissue. The follicles are almost filled with epithelial cells and often contain much 
gritty calcareous matter (acervulus cerebri^ brain-sand)y composed of microscopic 


particles, aggregated into masses and formed of earthy salts (phosphate and 
carbonate of lime, with a little phosphate of magnesia and ammonia) combined 
with animal matter. 

The same sandy matter is frequently found on the outside of the pineal body, or 
deposited upon its peduncles. It is found also in the choroid plexuses ; and in a 
scattered form occurs in other parts of the membranes of the brain. It occurs at 
all ages, frequently in young children, and sometimes even in the foetus. It cannot, 
therefore be regarded as the product of disease. The pineal body is larger in the 
child and the female than in the adult male (Huschke). In the brains of other 
mammals it is proportionally larger than in the human subject, and less loaded with 

The pineal body is developed originally as a hollow outgrowth from that part of 
the embryonic brain which afterwards forms the third ventricle ; the diverticulum 
becomes subsequently cut off from the ventricle, and undergoes ramification to form 
tubes which are afterwards separated for the most part into isolated vesicles. 

The pineal body is present in all vertebrates, Amphioxus only excepted. In 
elasmobranch fishes and in most reptiles, as the researches of de Graaf, Baldwin 
Spencer, and others, have shown, it is continued into a long tubular prolongation 
from the third ventricle, which passes through an aperture in the skull (parietal 
foramen) and ends under the skin in a small vesicle lined with ciliated epithelium. 
But in some reptiles {e,g,, Hatteria, blind-worm, lizard) this vesicle becomes 
developed into a structure which bears a close resemblance to an invertebrate eye 
(^pineal eye\ the part nearest the surface becoming thickened to form a kind of lens, 
and the part connected with the stalk becoming pigmented and stratified like a 
retina, whilst the stalk itself becomes solid and has nerve-fibres developed in it. It 
is doubtful how far this structure serves as an eye in any living reptile, but in 
certain extinct forms it was probably more completely developed. In birds and 
mammals the pineal eye is not developed, but the organ is similar in structure to 
that of man. 

The posterior perforated space (locus perforatus posticus) (fig. 32, x), 
lies in a deep fossa {fossa Taring His) at the base of the brain, at the bottom of 
which is greyish matter, connecting the diverging crura. It is perforated by 
numerous small openings for the passage of blood-vessels ; and some horizontal 
•white strias usually pass out of the grey matter and turn round the peduncles close 
to the upper border of the pons, entering which they reach eventually the medullary 
centre of the cerebellum (tcenia pontis). It corresponds posteriorly, as far as a line 
joining the anterior borders of the third nerves, to the floor of the aqueduct of 
Sylvius, but in front of those nerves to the posterior part of the floor of the third 
ventricle. In the grey matter over the space are a few scattered nerve-cells. 

The corpora albicantia or mamillaria (fig. 32, a ; fig. 86) are two round 
white eminences in front of this space, each about the size of a small pea, connected 
together across the middle line. Each corpus albicans contains grey matter 
concealed within its superficial white fibres, the nerve-cells being arranged in two 
groups, the lateral and mesial (nuclei of the corpus albicans) ; of these the lateral 
contains larger nerve-cells than the mesial. 

The white matter of the corpora albicantia is formed by the anterior pillars of 

the fornix : hence they have also been named bidbs of the fornix ; and by the bundle 

of Vicq d'Azyr, which enters the anterior part of each tubercle at the dorso-mesial 

aspect. Posteriorly each corpus albicans receives a bundle of nerve-fibres, which 

is termed its peduncle. This, which in man is concealed within the grey matter of 

the floor of the third ventricle, but which is seen at the base of the brain in many 

animals, and is connected with the lateral nucleus of the body, is traceable to the 

tegmentum and ultimately to the mesial part of the crusta (v. Gudden). In most 

vertebrates there is but one (median) corpus albicans in place of two. 

I 3 


An isolated bundle of one of the anterior pillars of the fornix is sometimee visible at the 
base of the brain passing to the corpus albicans (gtria alba tuberU, Lenhoss^). 

The tuber cinerenm (fig. 86 ; fig. 32, tx,) is a lamina of grey matter extending 
forwards from the corpora albicantia to the optic commissure, to which it is attached. 
It forms part of the floor of the third ventricle. In the middle it is prolonged 
forwards and downwards into a hollow conical process, the infandibiiliim 
(fig. 85, »), to the extremity of which is fixed the pituitary body. On its outer 
side close to the optic tract is a tract of grey matter with nerve-cells, termed by 
Meynert the hasal optic ganglion (see p. 119). According to Lenhossek this is 
distinctly subdivided into three successive groups of nerve-cells, the most anterior 
being just above the chiasma, the most posterior near the corpus albicans. 

The pituitary body or hypophysis cerebri (figs. 32, 39, h, and fig. 85), formerly 
called pituitary gland, from its being erroneously supposed to discharge piluita into 
the nostrils, is a small reddish grey mass, of a somewhat flattened oval shape, widest 
in the transverse direction, and occupying the sella turcica of the sphenoid bone. 
The pituitary body has a special prolongation of the dura mater completely 
enclosing it, except above where there is a small aperture for the passage of the 
infundibulum (see p. 182). The body consists of two lobes, of which the anterior 
is the larger, and is concave behind, where it embraces the smaller posterior lobe. 
The two lobes are entirely different, both in their structure and development ; and 
it is only in mammals that they come into close connexion witj:i one another. 

The posterior lobe is developed as a hollow downgrowth of the part of that cavity 
of the embryonic brain, which afterwards becomes the third ventricle. In the 
lower vertebrates, and especially in fishes, the cells which compose its walls become 
converted into nerve-cells and -fibres, and as the lobtis infundibuli it becomes an 
integral part of the brain. But in the higher vertebrates it remains small and 
almost undeveloped ; its cavity is obliterated, and all nervous structure becomes 
obscured by the ingrowth of vessels and of connective tissue into the now solid 
organ. The connective tissue forms reticulating bundles, between which occur 

Fig. 85. — Sagittal section of thb pituitary body and iNruNM- 



a, anterior lobe ; a\ a projection from it towards the front of the 
infundibulum, t ; 6, posterior lobe connected by a solid stalk with the 
infundibulum ; I.e., lamina cinerea ; o, right optic nerve ; oA, section 
of chiasma; r.o,y recess of the ventricle above the chiasma; cm., 
corpus mamillare. 

numerous spindle-shaped and branched cells, as well as a few larger corpuscles 
containing pigment-granules in their protoplasm. Sometimes remains of the 
original hollow are seen in the form of a cavity lined by columnar ciliated 

The anterior lobe^ darker in colour than the posterior, is developed as a tubular 
prolongation from the epiblast of the buccal cavity, with which it is therefore 
originally in connection, although it soon becomes separated by the growth of 
intervening tissue. In the adult it is constituted by a large number of slightly 
convoluted tubules or alveoli, similar to those of a secreting gland, and in like 
manner lined by epithelium, which in some cases fills up the tubule. The tubules 
are united by connective tissue, which is especially abundant in the neighbourhood 
of the larger blood-vessels, and also forms a sort of capsule to the organ. Moreover, 
portions of the tubules are frequently cut off by the connective tissue so as to form 
isolated vesicles. The outer layer of epithelium is columnar ; and in some of the 
larger tubes, especially those next to the posterior lobe, cilia may be detected on the 
cells. The blood-vessels are numerous, and the capillaries form a close network 


around the walla of the tnbules. The lymphatica of the organ originate in cleft- 
like spaces between the tubules and pass to a network In the capsule. In ita 
microscopic atrneture the anterior lobe of the pitnitarj body bears a resemblance 
to the thyroid body, the vesicles of which are also originally a network of anasto- 
mosing tabnles, and in some animals remain throughout life in this condition. 
Moreover, a colloid substance like that in the thyroid vesicles, ia found uometimes 
in the alveoli of the anterior lobe of the hypophysis. 

In the middle line of the base of the brain, in front of the optic oommisfiure, ia 
the anterior portion of the great longitudinal fissure, which separates the two 
hemispheres. At a short distance in front of the chiasms, this fissure is crossed 
transversely by the anterior recurved extremity of the corpus callosum. On gently 

Fig. 88. — OntOIN AND RSLiTWBS OF ... 

THi oPTio TiucT (G. D. Thuie). 
The parts &re liewed from betow, 
the mid-brain hATing been divided 
tiBjiarereely immeiliittelj above the 
pona, and the pons, cerebellum and ^ 
medulla obbngalA removed. The 
lower part of the figure u the more 

turning back the optic com- 
missure, a thin connecting 
layer of grey substance, the 

cupying the space between 

the corpus callosum and the 

chiasma, and continuous above 

the chiasma with the tuber 

cinerenm. It is connected at the sides with the grey substance of the anterior 

perforated apace, and forma part of the anterior boundary of the third ventricle 

(fig. 67, p. 70) : it is somewhat liable to be torn in removing the brain from the 

skull ; and, in that case, an aperture is made into the fore part of the third ventricle. 

The optic tracts and optic CDmmiBaTira orchiaamft. The optio tracts curve 
round the crusta on each side to unite with one another immediately in front of the 
tuber oinereum, where they form the X-shaped commissure which is known as the 
chiasma. The optic tracts form the posterior limbs of the X ; the optic nerves, 
passing into the optic foramina, the anterior limbs (fig. 8G). 

Each tract arises posteriorly by a broad root, which is divided by a longitudinal 
groove into two distinct parts, a lateral and a mesial. The lateral root is the larger. 
It is connected with and t;merges from the posterior and ventral part of the thalamus 
(lateral geniculate body and pulvinar), and is partly continuous with the brachium 
of the superior qnadrigeminal body. The mesial root, when traced backwards, is 
seen to curve round the crusta and then to lose itself beneath the mesial geniculate 
body, in which it appears to end, although it may perhaps ultimately pass into the 
inferior qnadrigeminal body as its brachium. Although this root appears connected 
with the internal geniculate body, it is doubtful if there ia any functional connexion 
between this body and the optic nerve, the part of the tract which enters the mesial 
geniculate body Ijeing Gudden's commissure, which joins the mesial geniculate bodies 
of the two sides (see below). Before reaching the chiasma the optic tract lies 
postero-mesially to the anterior perforated space, 

Darkschewitifoh describes the passage of some of the fibree of the optio tr»ob to the 
ganglion hobenulai and pineal pedonole, and ultimately bj the pOBterior commissuTe to the 
oculomotor nacleaB (compare pp. 109 and 114). Be regards these as fibres subserving the reflex 
changes of the pupO. 

As for the course of the optic fibres in the tract and chiasma it may be stated 


that although in many mammals (mouse, guinea-pig), and in all vertebrates beloM- 
mammals, the decussation is complete, so that all the fibres pass from one tract 
into the opposite -optic nerve, in other mammals (rabbit, dog, cat, monkey) and 
in man, it is incomplete, so that some of the fibres from the left optic nerve pass 
into the left tract and others into the right tract, and the same mutatis mutandis 
for those of the right nerve. This fact has been conclusively proved both by 
experiment and clinical observation. At the same time it ftiust be stated that cases 
have occasionally been recorded which, if correct, are only to be explained on the 
supposition that the crossing is complete : in these we must suppose that there has 
been a reversion to the lower and more primitive type of chiasma. 

The two sets of nerve-fibres are usually spoken of as the crossed and uncrossed 
bundles, although they are not to be regarded as formed into entirely separate 
funiculi, nor are their limits sharply defined either in the nerve, chiasma, or tract. 
The uncrossed bundle is distributed exactly to the lateral half of the retina, the 
crossed bundle to the mesial half ; and on the whole the fibres of the uncrossed 
bundle keep to the lateral side of the optic nerve, whilst the crossed bundle is on 
the mesial side of the nerve. In the chiasma and tract they are usually more 
commingled, and their relative position is veiy variously described. In a case of 
atrophy of one nerve which has been clearly described by Williamson, the uncrossed 
fibres chiefly occupied the middle of the tract, the crossed being chiefly at the 
periphery and lower part. Similar results were obtained by Henschen. 

Aooording to Salzer's enumeration, there are nearly half a million fibres in each optic nenre. 
The fibres vary in size. According to v. Gadden they are divisible, according to their calibre, 
into two classes, finer and coarser. The former of these he reganled as being concerned in 
the production, as afferent fibres, of the pupil-reflexes, the latter as conveying visual impressiona. 
The finer fibres degenerate after destruction of the anterior corpora quadrigemina (in the cat 
and rabbit). It must be remembered that not only afferent, but also efferent impressions are 
carried by the optic tracts ; governing the chemical changes which occur in the retina, and 
also the movements of some of its elements (pigment-cells, cones). 

Besides the optic nerve-fibres, there is a bundle at the posterior part of the 
chiasma, and running along the mesial side of the optic tracts to join the internal 
geniculate bodies of the two sides.^ This is known as the inferior commissure or 
commissure of Oudden. It appears to have no relation to the visual function, for it 
undergoes no change when the rest of the optic tracts become atrophied after extir- 
pation of both eyes in young animals. Its fibres are of extremely small diameter. 

In structure the optic tract resembles an extension of the white matter of the 
brain, being very soft and not divided up into bundles by connective tissue, nor are 
its fibres provided with membranous sheaths. These structures are found, however, 
in the chiasma, and in the optic nerve, which are strong and tough and invested 
with sheaths continuous with the pia mater and arachnoid. At its entrance into 
the orbit the optic nerve receives a strong investment from the dura mater, which 
is continued around it into the sclerotic coat of the eye. The nerve is subdivided 
by intercommunicating connective-tissue septa into a large number of compartments, 
which contain the nerve-fibres, but the latter are not gathered up into round funiculi 
invested by perineurium, as in the case of the ordinary peripheral nerves. 

Stilling has described the optic tract as sending a prolongation directly into the outer part 
of the cms cerebri. This prolongation is said to contain fibres which pass (1) to the oculo- 
motor nuclei ; (2) to the cerebellum by the inferior peduncle ; (3) to the pons Varolii, even 
extending to the inferior olive. 

The name tractus tranaversus pedunculi was given by Oudden to a band of fibres, first 
noticed by Inzani and Lemoigne, which is sometimes seen emerging; from the base of the 
anterior quadrigeminal body, and coursing obliquely over the brachia of the quadrigeminal 
bodies to enter the crus cerebrL It is much better marked in some animals than in man. 
It becomes atrophied after extirpation of the eye, and may be a part of the prolongation 
of the optio tract described by Stilling. 

i It is stated by Darkschewitsch, that this commissure unites each mesial genictdate body with 
the lenticular nucleus of the opposite side. 


Ab K^rds the course of the optic fibres, the results of esperiment show that 
whilst some have their cell-ofifrin iu the periphery— presumably in the nerve- cells 
of the retina — othere take origin in nerve-cella of parts of tiie brain (superior 
corpora quadrigemina, external geniculate body, and pulvinar). Of those nerve- 
fibres which have their cell-origin in the retina, and which, therefore, nndei^o 
degeneration backwards after section of the optic nerve or tract, some end by 
arborisations betweea the nerve cells of the external geniculate body and pulvinar, 
others by arborisations in the more superficial layers of the superior corpora quadri- 
gemina (see &gs. 70, 80, and 
87). It has been found 
that after enucleation of 
the eye the grey matter 
between the cells in these 
several parts nnde^oes 
atrophy. Those fibres which 
have their cell-origin in the 
nerve-centres end by ter- 
mioal arborisations within 
the retina. Their course 

will there be followed in i. 

the part of this work which 
deals with the structure of ; 
the eye. 

Finally, whilst dealing 
with the coarse of the 
optic nerve-fibres, it may 
be as well to mention the 
probable intercentral con- 
nections of the nervous 
visual apparatus. (l.)There 
ia iu all probability a donblc 
connection between the cor- . 
tex of the occipital lobe 
(which represents thehigher 
visual centre) and the lower 
visual centres of the thala- 
mencephalon and mesen- 
cephalon by two sets of 
fibres, one set arising from 

the cortex and passing 

through the corona radiata pig, sr.-DiAaum or ibi pbobabl. couui abd bilatiokb 
and caudal end of the in- of bomb or thb oitio »;BaBs. 

temal capsule, finding their 

terminal arborisation iu the grey matter of the lower optic centres, and another set 
arising in cells of those centres and finding their terminal arborisation in the 
occipital cortex. These connections are confined to the parts of the same side of the 
brain ; there is no evidence of any crossing of the fibres. (2.) There appears to 
be an intimate connection between the lower optic centres and the grey matter of 
the bulb and cord. This connection is probably mainly effected through the upper 
fillet. (8.) The nuclei of the nerves to the muscles of the globe of the eye, both 
external and internal, are certainly connected with the optic centres. It is possible 
that this connection may 'be partly effected through the posterior commissure and 
posterior longitudinal bundle ; it is probably both crossed and uncrossed : but the 


actual tracts of connection have not yet been elucidated. (4.) There appears to 
be a direct connection between some of the fibres of the optic tract and the cere- 
bellum, since after removal of one half of the latter organ, many of the fibres of 
the corresponding optic tract undergo the Wallerian degeneration (Marchi). This 
connection may also take place along the tract of the upper fillet. 

In the grey matter which lies between the third ventricle and the optic chiasma, 
a small collection of nerve cells (basal optic ganglion) is seen on each side, as already 
noticed (p. 116). These ganglia do not appear to have any direct connection with 
the optic nerve, as was supposed by Meynert to be the case, but from each a tract 
issues, which, after decussating with that of the opposite side {MeyiierVs commissitre)^ 
applies itself to the mesial side of the optic tract, close to Gudden's commissure, and 
passes backwards to the subthalamic region to enter the nucleus of Luys, and 
perhaps to be connected with the continuation of the npper fillet. Antero-laterally 
this tract may be connected, beyond the basal optic ganglion, with the lenticular 


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The lateral ventricles ; ventricles of the cerebral hemispheres. — An 

aperture (foramen of Monro) which has been already mentioned as opening but of 
the anterior part of the third ventricle (see p. U7) leads on each side into the 
corresponding ventricle of the cerebral hemisphere or lateral ventricle (figs. 88, 89). 
Each lateral ventricle is an irregularly curved cavity, extending in the substance of 
the corresponding hemisphere for about two-thirds of its entire length, and lined 
by a prolongation of the ciliated epithelium which characterises the inner surface 
of the true brain-ventricles. It may be described as consisting of a body, an anterior 
ham, a posterior horn, and a middte, lateral, or descending horn. The anterior horn 
curves from the foramen of Monro somewhat outwards, with a slight inclination 
downwards into the frontal lobe ; the body comprises that part of the cavity which 
extends from the foramen of Monro to its bifurcation into posterior and descending 
horns opposite the splenium of the corpus caliosum, and is separated anteriorly irom 
its fellow of the opposite hemisphere by a thin septum, the septum Itundum ; the 
posterior horn passes backwards, with a bold curve convex outwards, into the 
occipital lobe ; and the descending horn passes forwards and slightly downwards also 
in a bold curve with its convexity outwards, into the temporal lobe, and extends to 
about an inch from the apex of that lobe. The anterior horn is directly continued 
from the body of the ventricle, and may therefore be described along with it. 

The body and anterior horn of the ventricle are roofed over by the corpus 
caliosum, with its lateral extension into the substance of the hemisphere. In 
examining the ventricles from above it is usual to slice the brain horizontally down 
to the level of the caliosum, and then to cut through this commissure a short 
distance on each side of the middle line, and remove it sufficiently to expose the interior 
of the ventricle. The following parts are thereby brought to view, from within, out- 
wards, or laterally : {a) Theedgeof the fornix (figs. 88, 89,/), a flattened tract of white 
matter with longitudinal fibres, which lies immediately under the caliosum, broaden- 
ing behind as it passes under the splenium, and bifurcating in front into two 
cylindrical bundles, each of which passes over the foramen of Monro, and in front 
of that foramen into the mesial part of the subthalamic tegmentum, {h) If the 
caliosum and fornix are removed, a layer of pia mater is seen underneath. This is 
the velnm interpositom {fig, 94), and its edge projects as the choroid plexus of 
the lateral ventricle from beneath the margin of the fornix in the form of a 
vascular fringe (figs. 88, 89,^/. ch,), which extends from the foramen of Monro (at the 
back' of which it is continuous with the corresponding plexus of the opposite side as 
well as with those of the third ventricle) over the surface of the thalamus, as far as 
the descending cornu, into which it projects along the whole length of the horn 
(mesial border), {c) Lateral and anterior to the choroid plexus two masses of grey 
matter, separated by an obliquely-placed white stria, form the floor of the ventricle. 
The mesial and narrower of these is a part of the doi*sal surface of the thalamus (fig. 88, 
th, opt) ; it extends from the foramen of Monro to the posterior limit of the body of the 
ventricle and is covered with a thin layer of white matter. The white stria is the 
tania semidrcularis or stria terminalis (fig. 82,67.). A vein {vein of the corpus striatum) 
runs superficial to the tssnia, and passes in front, at the foramen of Monro, into the 
vein of Galen of the velum interpositum. Close to the ependyma and lying over 
this vein of the corpus striatum is a small greyish band, containing longitudinally 
running nerve-fibres : this has been named the lamina cornea. The lateral mass of 


Fig. 8S.— ViBW or tat latibaj. vchtiiiolr moH abovc. Xaturol nize. (G. A. S. kqcI Q. D. T. ) 

The preparation we« made with the brain in tUu (hardened). The skull cap and membraaea haciag 
be«n remoTsd, the brain traa sliced down to the level of the corpua callaauin. The left luteral vealriclc 
waa then opeped bj cutting away its roof, and the ialand expoaeil hy slicing awaj the opercula. The 
dnwiug ia made fraia a photograph. 

I.K., imnlaKeilii (the line points to the middle of the three gyri hreres) ; i.e., Kulcna centralis 
innlEe ; g.t., gjrus longus ideuIis ; c.c, corpus calloium ; n.L., nerves of Laaciiii ; lir.i., stria tecta ; 
/.mi., forceps miser ; f.mii,, fori;eps major; e.a., cama anlflriua of rantricle ; e.p,, comu posterius ; 
e.i., entrance to eornu inferios ; /.if., foramen Honroi ; a.M., buIcub leading backwards to the foramen 
Honroi ; e.itr,, corpus atriatnm ; iA.opt,, thalamus opticoB, anterior tubercle ;, pleius cboroides ; 
/, fornix ; f, ila anterior pillar ; h, posterior end of hippocampus major ; Iri., trigonum ventiiculi ; 
ot^ear, catcar aris. 


grey matter is the nucleus caudatus of the carpm striatum (c. str.) It is pear-shaped, with 
the larger end projecting into the floor of the anterior horn, and the smaller tapering 
posterior end (tail) extending to the origin of the descending horn, and then curving 
downwards and forwards along the dorsal part of this horn, in which it forms a 
long, narrow, rounded eminence. The posterior horn (figs. 88, 89, c,p.), which 
is curved around the parieto-occipital fissure, its concavity therefore being 
directed inwards, passes, as before said, into the occipital lobe. It is roofed by the 
fibres of the corpus callosum which are passing to the temporal and occipital lobes : 
part of these fibres also form its lateral wall. At the upper part of its mesial wall 
there is a bundle of fibres (forceps major) sweeping round from the splenium of the 
callosum to enter the occipital lobe. This produces a projection into the cavity of 
the horn, which is known as the bulb of the posterior horn. Below it is another 
curved eminence, which extends from the base of the horn backwards for a variable 
distance, to end in a pointed extremity : this is termed, from its resemblance to a 
cock's spur, the ergot (Morand), or cakar avis (also hippocampus minor). It 
corresponds with the calcarine fissure on the mesial surface of the hemisphere. 

The hippocampus minor is not peculiar to the human brain as was at one time thought, but 
is found in the brains of quadrumana. In the human subject the posterior horn varies 
greatly in size, and the hippocampus minor is still more variable in its development, beinf? 
sometimes scarcely to be recognised, and at others proportionally lar^e. It is usually most 
developed where the posterior horn is longest; but the length of the posterior horn, and 
prominence of the hippocampus minor, are by no means in proportion to the dimensiouB 
of the hemisphere. 

The middle, lateral, or descending horn (fig. 89) is directed at first back- 
wards and outwards from the posterior end of the body of the ventricle ; it then 
passes downwards and forwards with a bold sweep (at about the plane of the parallel 
sulcus), being finally curved inwards, and ending about an inch from the apex of 
the temporal lobe, where it abuts against the amygdala. The dorso-lateral boundary 
(roof) is formed by the fibres of the callosum, which are arching over it into the 
temporal lobe, forming the so-called tapetum. The tail of the nucleus caudatus 
and the taenia semicircularis are prolonged into the roof. Extending along the floor 
of the horn is an eminence known as the hippocampus major or comu Ammonis (fig. 
89, A), which becomes enlarged as it descends, and being notched, its edge here 
presents a certain resemblance to an animal's paw {pes hippocampi). This eminence 
corresponds with the hippocampal fissure externally, which thus indents the floor 
of the cornu, and the grey matter at the bottom of the fissure being separated from 
the cavity of the ventricle by a thin layer of white substance (covered with ependyma), 
shews through and gives a bluish-white appearance to the hippocampus. Mesial to 
the hippocampus is the white band known as the fimbria (fig. 89,^), prolonged from 
the posterior pillar of the fornix ; and over the fimbria, at the angle which the floor 
of the horn here forms with its roof, the choroid plexus projects into the cavity from 
the external pia mater ; the plexus is, however, covered by the epithelial lining 
of the cavity which extends over it in passing from roof to floor. If the pia mater 
is pulled away it drags aloug with it this covering layer of epithelium, and the cornu 
is made to open on the mesial surface of the brain. A cleft-like opening is thus 
produced, which has been called the inferior fissure of the cerebrum^ being the 
lower part of the so-called transverse fissure, which follows the plane of the velum 
interpositum (see p. 184) over the thalamus and third ventricle, and emerges over 
the corpora quadrigemina. It is along this fissure that the choroid plexuses of the 
pia mater are invaginated into the ventricles, covered by the ventricular epithelium, 
which is pushed in before them. It is only when the choroid plexuses are dragged 
away that an actual fissure is formed in the hemisphere-wall between the fornix 
and fimbria on the one side and the optic thalamus on the other ; but with the 






Natural aiM. (E. A. S. and G. D. T.) 

This u ft farther (liga«<!Uon of tbe preparation Bhown in tig. 88. The ineula hu been sliced avsy 
and the middle or descending cotnu, c.i., ciposed. Within thin are Been the following parts: ;t, fimbria, 
contjpned from the fornix ; k, the hippacampus major ; eoU., the eminentia collateralu. The other 
letteriDg ai in fig. 8S. 


plexDB m ailu it is a deep snlcnB, i.e., an invagination only, of the thin hemisphere- 
wall (here fonnedof the ventricular epithelium alone). It is known as the choroidal 
fissure, and appears at an early period of embryonic development. 

Herkel and Mienejewekj have deecribed an actu&lcteft in the pia mater along the descend- 
ing hom which effects a communication between the ventricle and tiie Bubarachnoid space, 
analot^ons to the foramen of Majendie and the lateral apertures in the fooitb ventriole. Thia 
observation has not hitherto been confirmed. 


(After Welcker.) 
A, from above ; b, from the «de. The projections into the cavities of the 
bound the ventricles are seea u impreauDU upon the cast. 

At the jnnction of the descending with the posterior coma, and occnpying the 
angle between the hippocampus mnjor and the calcar, is a triangnlar space, the 
fioor of which is mainly occupied by a smooth, somewhat raised surface, which 
extends backwards into the posterior comu, and is often continued downwards into 
a longitudinal eminence which passes for some distance in the inferior bom alongside 


of and lateral to the hippocampna major. This eminence con'esponds with the 
collateral figgnre externally, and is known as the eminenfia collateralis or pe» accea- 
aoriua (fig. 89, coll.) ; this term is also by some anthors used to include the smooth 
eminence at the junction of the cornaa. The triangnlar space at this junction is 
termed by Schwalbe trigonum fmtrieuli. 

The shape of tlie vectricles is best shown in a cast of the cavities, which can be 
made in plaster of Paris. The appearance of such a cast, viewed respectively from 
above and from the side, is given in the accompanying figure (fig. 90, A, b). 

The corpus oallonim or great oommusnra (trabs cerebri) (figs. SI, 92, 102), 
a white structure, about 10 centiraetere long, which connects the two hemispheres 
throughout nearly half their length, approaches closer to the front than the back of 


the hemispheres. It is abont 20 mm. in width behind, and somewhat narrower in 
front. Its thickness is greater at the ends than in the middle, and is greatest 
behind (8 mm.). It is arched from before backwards, its lower sur&ce being 
concave and its upper surface convex. Its upper surface is distinctly marked by 
transverse furrows, which indicate the direction of the greater number of its fibres. 
It is also marked in the middle by a longitndinal furrow (raphs), which is bounded 
by two white tracts, placed close to each other, named the mesial longitudinal slritt 
or nerves of Lancisi (fig. 88). On each side, near the margin, are seen other 
longitudinal lines (grey or lateral longitudiTial atria). The lateral striee lie within a 
fissure {calhsaljksure) which separates the upper surface of the commissure from 
the gyrus fomicatus (by which convolution they are entirely covered in ; hence the 
name, Umia lecbs, which is often applied to them). Both the mesial and lateral 
longitudinal strife are traceable, when well developed, into the gyms dentatus 
posteriorly. The morphol<%ical value of these structures will be afterwards referred 
to (p. 155). 

In front, the corpus callosum is refiected downwards and backwards, forming a 


bend named the ganu (fig. 91). The inferior or reflected portion, which is named 
the rostrum, becomes gradnalij narrower as it descends, and is connected with the 
lamina cinerea bj a thin white layer, the commUsura baseos alba of Henle. It gives 
off also two bands of white substance, the peduncles of the corpus callesum, which, 
diverging from one another, ran backwards across the posterior margin of the 
anterior perforated space on each side to the tip of the temporal lobe, where they 
meet the inner olfactory roots. These peduncles traced upwards around the genu 
are fonnd to be continued into the mesial longitudinal strife. 

Behind, the corpos catlosum terminates in a iree thickened border, named the 
gplmitim, but this term is sometimes restricted to the under part of this thickened 
border, which appears as if rolled roand under the rest {splenium proper, Beevor). 

Pig. S2. — ViBW OF TBt coHPUs CALLOSUM FBOH ABuVK (from Sappey after Poville). \ 

The uppei Burfoce of the corpus c&llosum has been fuUy eipcesd by Bepaistiiig the cerebral hemi- 
BpliereB and throwing them to the side ; tho gjnia fornicatiia has be«n partly detached, and the trang- 
venie fibres of the corpus ealloBum tnced for eome distance into the cerebml medullary subatancc. 

1, the upper surface of the corpus cailoBum ; 2, median furrow or nphe ; 3, longitudinal stns 
bounding the furroir ; 4, swelling formed by the trajisverse banda as they pass into the cerebrnm, 
tircbing over the tide of the lateral ventricle ; 5, anterior eiCremlty or knee of the coqms calloeum ; 6, 
poalcrior extremity ; 7, anterior, and 8, poalerior fibres proceeding from the corjiue oillosam into the 
frontal and occipital lobes respeclively ; 9, margin of the awelling ; 10, anterior pai-t of the gyms 
fomicatua ; 11, fissure between the corpus callosum and this convolution opened out ; outtide 12, is tbe 
termiDstien of the callUBo-muginal Gaaure, and before 13 is the parieto-occipitol fissure ; 13, upper 
■urCtice of the wtcbellum. 

The mesial part of the under surface of the corpus callosum is connected behind 
with the fornix, and in the rest of its length with the septum lucidum, a vertical 
partition between the two lateral ventricles, which is included in the anterior bend 
of the corpus callosnm. On the sides the corpns callosum roofs in the body and 
anterior horn of the lateral ventricles. The enlai^d posterior part or splenium lies 
over tbe mcBencepbalon, with pia mater between. The transverse fibres of the 
corpus callosum pass in a radiating manner, interlacing with those of the internal 
capsule, through the medullary centre to the cortex of each hemisphere. Those in 
front which sweep round into the prefrontal region form the so-called forces minor. 


Those from the body and the upper part of the splenium which cnrve over the 
lateral ventricle form the tapetum, whilst a large mass of fibres from the 
splenium proper curves round into each occipital lobe and is known as the forceps 

The septum Incidum (fig. 91, sept luc,)y a thin double partition, separates the 
anterior part of the two lateral ventricles. It is composed of two distinct laminae, 
having an interval between them {ventricle of the septum) which contains fluid 
probably of the nature of lymph. It occupies the interval between the corpus 
callosum above and in front, and the anterior part of the fornix behind (fig. 91) ; 
and gradually tapers backwards to end over the middle of the third ventricle, from 
which it is separated by the fornix and velum interpositum. Antero-inferiorly it 
extends downwards in an angle which reaches the anterior commissure. 

The laminaB of the septum are formed of a part of the mesial wall of the hemi- 
spheres which has remained free, while the surrounding parts have become united 
by the development of the corpus callosum above and in front and the fornix 
below and behind. The ventricle of the septum was therefore originally a part of 
the great longitudinal fissure, and has no connection with the internal ventricular 
cavity of the brain. Accordingly we find that it is not lined by ciliated epithelium, 
but each lamina consists of a thin layer of grey matter next to the cavity, and 
homologous with the grey matter of the cerebral cortex, and a thicker layer of 
white matter continuous below on either side with the general white matter of 
the hemisphere. Externally, next to the lateral ventricle, is a layer of ependyma, 
and covering this the epithelium which lines the lateral ventricle ; internally is a 
layer of connective tissue, homologous with the pia mater. 

The fomiz (fig. 91, /) is an arched longitudinal white tract consisting of two 
lateral halves, which are separated from each other in front and behind, but in the 
intermediate part are joined together in the median plane. The two parts in front 
form the anterior pillars (columrm fornicis) ; the middle conjoined part is named the 
body ; and the hind parts, which are again separated from each other, form the 
posterior pillars {crura fornicis). 

The body of the fornix is triangular in shape, being broad and fiattened behind, 
where it is adherent to the under surface of the callosum, and narrower in front, 
where it is attached to the septum lucidum. Its lateral edges are free and are seen 
projecting into the lateral ventricles just above the choroid plexuses. Its under 
surface rests upon the velum interpositum, which separates it from thp optic thalami 
and the third ventricle (fig. 94). 

Beevor distingaishes (in the monkey) two sete of fibres in the body of the fornix. Of 
these, the mesial set, when traced backwards, appear to tarn dorsally and pierce the corpus 
callosum just in front of the splenium ; above the corpus callosum they may perhaps join the 
Ix>sterior fibres of the cingulum (see p. 158), but their actual destination has not been certainly 
followed out. 

The anterior pillars (fig. 82, Of), cylindrical in form, can be traced downwards, 
slightly separated fix)m each other, in front of the foramina of Monro, of which 
they form the anterior boundaries, and through the grey matter on the sides of the 
third ventricle, curving backwards to the corpora albicantia. There each column 
turns upon itself, making a twisted loop which forms the white portion of the 
corpus albicans, and from this it appears to be continued, as the bundle of Vicq- 
d'Azyr, upwards into the anterior nucleus of the optic thalamus (fig. 93). Each 
pillar is connected near the foramen of Monro with the stria pinealis (taenia 
fornicis), and with the taenia semicircularis, and it gives fibres to the septum 
lucidum (for other connections of the anterior pillar, see p. 158). 

According to the experiments of Gudden and Forel the fibres of the anterior 

VOL. in. K 


pillars find a terminatioa in the grey matter of the corpora albicantia, and are not 
directly continuous, as in dissected preparations they seem to be, with the bundle of 

The poslerior pillars or crura of the fornix (fig. 94, IS) are the diverging 
posterior prolongations of the two flat lateral bands composing the body. At first 

Pig. 63.— Sketch hhowirq tbi oEiaiK and cok- 

DiDved at its aatcrior ami lower part as far as a. 
(A.J, upper part of the thalamuB ; rk.m, it^ mesial 
surface : between the tiro ii the medullanr stria, 
leadJDg from the pineal gland anil IriganumhabeDuIi;. 
ly.h, to tJie anterior pillar of the foraiii, c.f; f, 
bundle of Vicq-d'Aijr ;, corpus mamillare ; 
?'./, flbiva oE the inferior peduncle of the thaluniu 
diTorgiog iu its aubstance ; eo.a, anterior commi>- 
aama ; i, infandibuluni ; r.ji, stalk of pineal body ; qu, caipora 

they adhere to the under surface of the corpus calloBUtn, then, curving outwards and 
downwards over the pulvlnar of the optic thalamns, each cms enters the descending 
horn of the lateral yentricle, where some of its fibres are distributed on the surface of 

BiRTATi. (From Sappe; after Vicq- 

dA.,,.) I 

1, fore |nrt of the tela rhoroidea 
or re1un:i inlerpositum ; 2, £, choroid 
plexus : 3, 3, left vein of Ualen partly 
eovered by the right; A. anterior 
pillnra of the fornix divided in front 
of the foramen of Monro ; on either 
side are seen small veine from the 
front of the corpus calloeum and tlie 
neptum luciiium ; 5, vein of tbe 
corpus striatum ; 6, convoluted 
marginal vein of the choroid pleios ; 
7, vein rising from the thalamus opti- 
cus and corpus striatum ; S, vein 
proceediug from the inferior camu 
and hippocfiuipue major ; S, odc from 
the posterior cornu ; 11, fornix 
divided near \\x middle and turned 
^ backwards ; 1 2, lyra ; 1 3. posterior 
pillar of tbe fornix ; 14, thesplenium 
of the corpus callosum. 

the great hippocampus and 
the remainder are prolonged 
as the narrow band of white 
matter kuown as the iania 
hippocampi or fimbria (fig- 

On examining the under 
surface of the conjoined posterior parts of the fornix and corpus callosum, the 
splenium of the latter with its thickened edge and the diverging halves of the 
fornix appear to enclose between them a triangular structure, marked with traus- 
verst^ longitndtnal, and oblique lines. To ibis part the term lyra has been applied 


(fig. 94, IS!). ThiB coutaioB n few fibres which paee acroBS from one posterior piiiav 
of the fornix into the other, and ate considered to form a commissutal connexion 
between the two hippocampal regions of opposite sides. This connexion is denied 
b7 Beevor (in the monkey). 

The tnnia Mmicironlaris is & band of white matter which lies in the groove 
separating the ventricular surface of the nnclons candatus from that of the optic 
thalamus. It extends from the extremity of the descending horn of the lateral 
ventricle, where it passes into the nucleus amygdala, to the anterior part of the 
body of the ventricle, as far as the foramen of Monro, having a curved course corre- 
sponding with that of the ventricle. Its anterior connexions are soraewhat obscure, 
but, according to Schwalbe and Testnt, it divides anteriorly into two parts, one of 
which is continued into the anterior pillar of the fornix, and the other passes over 
and in front of the anterior commissure to become lost in the grey matter which 

Fig. 95. — COKOK*! SBCTIOS 

(Key and Retziiu.) 

e, c, coipns caltoBum ; belair its 
middle part the Beptum lucidnm, 
■ad belov thnt agaiD tfae fornix ; 
J.V, lateral ventricle; Ch, tbala- 
mas; between the two thalami 
the tbinl Tentricle is seen ; below 
the thnlamog is cbB eubetantia 
innomiData ; itr, lenticular nu- 
cleus of the carpoB atriatuni , 
G, candate uurIeub of tlie same ; 
biBtween th and tir is tlie inteniHl 
GApSaie ; outside tlr is tbe thin 
gre; band of the claustrum, and 
Dutude this again the isiaiid ol 
Beil at tbe boltom of the SylvUi> 
fiaauie ; n, n, ducIgus amygilalE; ; 
immedtatfily within tliis is the 
optic tract seen in section ; p, 
piluilacy body ; B, body of tbe 
sphenoid boae : fo, subMscbnaid 
sjiace i V, villi of the arachnoid. 

intervenes between the septum Ineidum and the auterior end of the nucleus 
caudatus : some fibres perhaps penetrating into that nucleus. According to Foville, 
each extremity is ultimately traceable into the anterior perforated space. 

The corpora striata [yamjlia of lite eerebi-al hemisjiheres), situated in front and 
to the outer side of the optic tlialami, are two lai-ge ovoid masses of grey matter, the 
greater part of each of which is embedded in the white substance of the hemisphere 
(extraventricular portion), whilst a part becomes visible in the body and anterior 
horn of the lateral ventricle (intraventricular portion). The corpus striatum derives 
ics name from the streaked appearance it presents, especially in its anterior part, 
when cut into, an appearance which is due to the passage through it of bundles of 
white fibres of the internal capsule to the frontal lobe of the hemisphere. 

The nnolans candatus {intraventricular portion of the corjms striatum) (tig. 82, 
Oa. ; fig. 88, cslr.), is of pyriform shape, its larger end being turned forwards and 
appearing in tbe fioor and partly in the lateral wall of the anterior horn. This 
enlarged anterior extremity projects into the white matter of the frontal lobe, where 
it is bounded by the fibres which pass from the genu of the cailoaum. Its narrow 
end is prolonged backwards and outwards along the body of the ventricle and into 
the roof of the descending horn, passing nearly to the extremity of the latter. The 
candate nucleus is separated from the thalamus by the teenia semicircularis. Where 
it hes in the lateral ventricle (superior surface) the nucleus caudatus is covered by a 


layer oF ependjma and over bhis by the ciliated ventricular epithelium. The ganglion 
is itself composed of a reddish grej substance like that of the outer zone of the 
lenticular nucleus (see below). On the deeper side, that turned towards the internal 
capsule, the nucleus receives from this a number of bundles of medullated fibres 
which are traceable from the crusta. According to Wernicke it is doubtful if any of 
these'pass on to the white matter of the hemispheres, nor do they come ^m the 


QENO or TBI OOMVI C1LLC8D1I. (B. A. S.) Ftoid a phatagnph. 

g.c.c, gena corporis eollosi ; e.a., carnn auUrins of Ut«ni1 ventricJe bounded kteratly b; the grtj 
mau oE the carpus strutmn ; cl., cIsDBtrum ; i.Jt., jnauls ; Sg., Sjlvlan finura ; c-in.i., enlcua Ralloso- 
la&rglnalis ; i.f.i., sakui frontalis superior; t./.i., eutcus preceatralia; i,olf., suicos olfactorius ; 
fr.ori/., orbital Burface of froDtal lobe ; tr.olf,, tractiu oltaclflriuB in section. 

Tbs section posses a litUe more anteriorly through the left hemisphere than throngh the right. 

crnsta directly, but only after traversing the medullary laminae of the lenticular 
nucleus (see below). 

The nerve-cells of the nuclens caudatus are multipolar, and, in the adnlt, pig- 
mented. Some are moderately lai'ge, but most small, belonging to Golgi's seQond 
type, with short axis-cylinder process (Marchi). Their Berve-procesBes pass in 
variouB directions, some into the internal capsule. In addition, peculiar spheroidal 
cells containing two or more nuclei were described by Henle. 

The nuolsua leaticularia (exlrarenlricular portion of the corpus striatum) is 
separated in the greater part of its extent from the intraventricular part by a layer 


of white substance (mlernal capsule), bnt is united with it in front, where it is 
pierced, as just stated, by the fibres passing to the Iroatal lobe. The lenticular 
nucleus is only seen in sections of the hemisphere. Its horizontal section (fig. 99, «./) 

(E. A. 8.) From a photograph. 

e.e., eorpOB callmnm ; /o., interior pillan of tbe fomiic with the Anterior eitremit; of the third 
T«ntricle between them ; u.l., lateral Tentrioles ; o.r., anterior commissure ; n.c., nucleus caudiitus ; 
ffl.p., gXuhaa pallidus and pti,, putsmen, o! nucleus lentkulnrts ; c.i., between the ddcIsub caudnttts 
and nucleoB lenticalaris, the mternal capaulB ; d., dauatrum ; i.R., inaula ; c.m.a., bdIcub calloao- 
marginalis ;, BnlcuB frontalis superior;, huIcub precentralis superior; tr.nif., traotna 
olfactorius psasing to tbe anterior perforated i>pace and giving off its mesinl, lateral, and middle roots. 

somewhat resembles that of a biconvex lens, being wider ia the centre than at either 
end, but larger anteriorly than posteriorly. It is less extensive than the caudate 
nucleus, which projects beyond it at either end. The antero-posterior diameter 
corresponds closely with that of tbe ceotral lobe of the hemisphere, or island of Reil, 
and the greatest width is opposite the anterior edge of the optic thalamus. On a 


transverse rertic&I section through the middle (figs. 97 and 98), this nnclens appean 
triangolar, having a lateral, a mesial and an inferior turface, facing respectively the 
external capsule, the internal capsule, and the base of the brain. Two ivhite lines 
{medullary lamitue), parallel to the lateral border, divide it into three zones, of 
which the outer [puiamen, Bardach, figs. 97, 98, pv.') is the largest and of a dark 


BiHiND THK oi^ic cuiAsuA. (E. A. S. ) Piam > phoUgniph. 
c.c, carpus callasum ; /u.,bodj of fornix: ///., third ventricle ; v.l,, lateral ventricle ; n.c, nneleiu 
oaadHtua ; tlr.m., stria mcdullaria ; tk., thalainiiB ; n.'i., internal capeiile ; Jjl-p-, globuH pallidus ; pu., 
putamen ; c.t., eiternol capsule ; d., clniutrum ; i.K., iaaiila ; ■n.amj/g., nucleus amfgdalia ; A, anterior 
end of hippocampiu major projecting into tbe deacen ding corao of the lateml ventricle ; tr. , optic tract ; 
•■A., optic chiuma ; ii.o;i(., optic nerve ; c-ni.i., cHllononiBiginal sukns: Ao.i., Kolandic sulcus ; in-p.t,, 
iatraparietal sulcus; Sy., Sylvian tissure ; ji/f.i., parallel fissure i iii/lf.!., second temporal sulcai j 
coU.1., collateral sulcus. 

reddish colour marked ivith fine radiating white Etnie, whilst the inner two, known 
conjointly as the ghbtu pallidus {glp.), are yellowish in tint. On its outer side is a 
grey lamina, termed the claustrum {cl.\ which ie separated from the lenticular nucleoB 
by the stratum of white subBtance named the external atpmle (c.e.). The internal 
capsule (continnation of the crusta) separates it in the greater part of its extent 
from the candate nnclens and thalamus, but anteriorly the two nuclei of the corpns 
Btriatnm are united at their bases. Where it is widest (fig. 97) the lentioolar 


nnclens is continuous below with the anperficia) grey matter forming; the anterioi' 
perforated lamioa, into which the base of the clauBtram also passes, and further 
back it comes in contact below with the nucleus amygdalie (fig. 98) ; through 
these fltructnres it is continuons with the grey cortex of the hemisphere. 

All three zones of the nucleus lenticularia are pervaded by bundles of white fibDw. 
but they are most conspicuous iu the outer zone. The grey matter between the fibres 
contains many cells with yellow pigment in them. Thft cells on the whole resemble 
those of the caudate nucleus, but there are more in proportion belonging to the first 
type of Golgi (cells with a long nerve-process). Fibres pass directly from the 
inner zone into the adjacent part of the inner capsule (i.e., into the peduncle of the 
cerebrum), while others from the substantia innominata below the optic thalamus. 


preparation by Mr. IS. U. Shattock. } Natural aiie. ' 
Tha section ii riewed from holow : i:l, lateral 
ventride, anterior cornu : c.c, corpus calloaum ; 
i.^ septum lucicluni ; «./, anterior pillars of the 
fomii : D 3, third ventricle ; CA, tbalsmus opticus : 
It, atria terrninalis ; e, nucleus caudalua, and n.l, 
DUcleuB lenticutaris of the corpus striatum ; i.c, in- 
ternal capsute ; ff, its angle or genu ; n.c, tail of tfae 
nncteus caudatus appearioR in the descending eomu 
of the lateral TenlriclB ; el, claustrum ; 1, island of 

curve outwards aronnd the mesial edge of 
the peduncle and enter the lower part of 
the lenticular uuclens as a distinct bundle 
(ansa lenticularis, p. 112) and passing into 
its medullary laminie are distributed iu the 
middle and outer zones. 

Other fibres connect the caudate with 
tbe lenticularnucleuB, and others again pass 
from this nucleus into the corona radiata 
or white substancu of the hemispheres and 
thence to the cortex, but few fibres emerge 
from or enter the lateral surface of the 
lenticular nucleus, which is sharply marked 
off from the external capsule. 

The extonul capanla is formed of fibres which are not directly connected with 
the lenticular nucleus but are derived partly from the anterior commissure, and in 
part from a portion of the ansa lenticularis. 

The olawrtnuu (figs. dC to 100,c/)iBathin lamina of grey matter which is smooth 
next to the outer capsule but ridged and furrowed externally, the ridges and furrows 
corresponding to the gyri and sulci of the central lobe, with the white substance of 
which the claustrum is in immediate relation. According to Meynert the claustrum 
is to be looked upon as a separated part of the grey cortex of the central lobe. In 
transverse sections of the hemisphere the claustrum is seen to taper to a fine thread 
superiorly (apex) and to expand below (base), having the shape of an elongated 

In the claustrum the cells are for the most part small and spindle-shaped, and 
arranged parallel with the surface, resembling those which are met with in the 

' This figure shows the narrowed connections of the island of Reil with the rest of the bemiipher* 
{mantle). These oarmw connecting parts have been teimed by tialdbeig ittkmi (anttrior etfoitenor) 
lobi ceMralU. 


deepest layer of the grej cortex of the hemispheres. Most of the cells coDtain 
yellow pigment. 

The internal capnle (Burdach) (figs. 97 to 100, c.i. and i.c.) is a Inmellated 
tract of white fibres which lies between the nucleus lenticularis laterally and the 
nucleua candatns, stria terminalia, and optic thalamas mesially. It is somewhat 
interrupted, eapeciallj in iront, by strands of grey matter which nnite the caudate 
and lenticular nuclei. In front, behind and above it ia continuous with the white 
substance of the hemispheres, its fibres diverging in a fan-like manner towards the 
cortex {corona radiala of Reil). Below it passes directly into the crusta, of which it 
is the immediate coutinuatiou. In horizontal sections (fig. 99) the internal capsnlc 
shows a bend (genu) opposite the stria terminalia, the anterior third forming an angle 
of about 120° with the poaterior two-thirds ; these two parts are known as the anle- 
rioT and posterior segments respectively. In vertical sections (fig. 100) it appears 
to take a straight course, upwards and outwards from the crus cerebri to the 

Pig. 100.— Skctior AC boss thb onic 

Natural ai 

ik., tbaUmus ; a, t. i, its anterior, 

extsronl and inUmitl iiuclft rcsi^ectively ; 

w. iU latticed lajer ; m.c, miticile eoni- 

miesure ; ahovc anJ below it ia tlie cavity 

of tha third ventricle ; t.t., corpns callD- 

sum ; /, fomii sepant«d Troia the tbinl 

ventricle and thalamus by the Telnm 

iuterjiOBituiD. In the middle of this are 

seen the two veins of Galen and the 

thoroid plexuses of the third ventricle : 

iind at its edges the choroid plexuses of 

the lateral yeniricles ; f.]., tienia eemi- 

clrculiriB ; cr., forward prolongation of the inista passing laterally into the intei-nal capsule, I'.r. : 

i.t.c., subthalamic prolongation of tha tegmentum, consisting of (1} the dorsal layer, ('J] the uina 

inceita, and (3) the nucleus of Luys : i.n., Bubstantia nijtra ; n.r., nucleus caudatus of the corpus 

■triatnm ; n.l,, nncleus lenticularis ; r.c, external capsule ; d., claustrum ; J, island of Keil. 

corona radiata. It has been determined as the result of experimental observa- 
tions in animals, and from pathological and clinical obsen'ations in man, that the 
fibres which course in the middle third of the internal capsule (i.e., which are 
opposite the globus pallidus of the leiiticnlar nucleus) are connected with the part 
of the cerebral cortex excitation of which gives rise to movements in the various 
parts of the body (Rolandic region of cortex), whilst those of the anterior third 
aro connected with the prefrontal region, and those of the posterior third with the 
occipi to- temporal region. 

Besides these fibres which connect the cortex of the hemisphere with the crusta, 
the internal capsule contains others derived from various sources, viz., from the 
o<iudate and lenticular nuclei, the optic thalamus, and snb-thalamic region, and 
also, through the corpus callosum, Irom the cortex of the opposite hemisphere 
(Hamilton). The exact localization within the internal capsule of most of these 
fibres has uot as yet been determined. 



The cerebral hemispheres together form an ovoid mass, flattened on its under 
side^ and placed in the cranium with its smaller end forwards, its greatest width 
being opposite to the parietal eminences. The hemispheres are separated in a large 
part of their extent by a deep fissure, the great longitudinal fisHXtre, On opening 
this fissure by drawing asunder the two hemispheres, it is seen, both before and 
behind, to pass quite through to the base of the cerebrum ; but for 10 centimeters 
in the middle it is interrupted at a depth of about 30 mm. at the front to 40 mm. 
at the back by a large transverse mass of white substance, named the corpus callosum, 
which connects the two hemispheres together. While the brain is within the skull, 
the longitudinal fissure is occupied by a vertical process of the dura mater — the falx 
cerebri — which dips down between the two hemispheres, not quite reaching to the 
corpus callosum in front but touching it behind. 

Each cerebral hemisphere has an outer, convex surface, in contact with the vault 
of the cranium ; an inner or mesial, flat surface, which forms one side of the 
longitudinal fissure ; and an irregular under surface, in which is a deep cleft, the 
vallecula Sylvii. In front of this cleft the under surface (orbital division) rests in 
the anterior fossa of the base of the skuU^ behind it in the middle fossa (temporal 
division), and further back still, on the tentorium cerebelli (occipital division). The 
surfaces pass into one another at the borders, which are also three in number, viz. : 
two mesial (superior and inferior) and one lateral. The anterior extremity of each 
hemisphere is known as the frontal pole, the posterior as the occipital pole. 

The surface of the hemispheres is composed of grey matter, and is moulded into 
numerous smooth and tortuous eminences, named convolutions or gyrij which are 
marked off from each other hj fissures or sulci of varying depth. 

The convolutions are covered closely throughout by the vascular investing 
membrane, the pia mater, which sends processes down to the bottom of the sulci 
between them, while the arachnoid membrane passes from one convolution to another, 
without dipping between them. In general, the height of a convolution exceeds its 
width ; and its width at the surface is somewhat gi*eater than at its base. The 
convolutions present considerable variations of position, direction and complexity in 
the brains of different individuals, and even in the two sides of the same brain, but 
they are usually recognizable without much difficulty. It is far easier, however, to 
trace the more important fissures and convolutions on the brain of a monkey, where 
they are much less obscured by tortuosities and secondary sulci. 

Since the external grey or cortical substance is continuous over the whole surface 
of the cerebral hemispheres, being found alike within the sulci and upon the gyri, it 
is obvious that a far greater extent of grey matter is thus provided for with a given 
size of the brain, than could have been the case had the hemispheres been plain and 
destitute of convolutions ; indeed, it is calculated that the extent of " sunken *' 
surface is twice that of " exposed" surface {cf, pp. 176, 177). 

The sulci between the convolutions vary greatly in depth, being in some parts 
quite shallow, in others as much as 25mm. (1 inch) or more deep. The average 
depth is about 10mm. or 12mm. Certain well-marked sulci can easily be recognized, 
and these serve as guides to the position of others which may at first be less readily 

It may be well in the first instance to describe the six chief or " interlobar " 
fissures, so-called because they are used to mark the hemisphere off into lobes ; the 
lobes themselves, with the convolutions and fissures which are included within 
them, can then conveniently be taken in order. 







Fig. 102. — Mesial aspect of the left hemisphere of a sixplt oonyoluted European brain. 

(E. A. S.) 

Fig. 103. — Under surface of a simply conyoluted European brain. (E. A. S.) 

The above are depicted nearly of the natural size. They have been drawn from photographs, and are 
all taken from different specimens. 

The sulci are marked with small italic letters ; the gyri with italic capitals. The corresponding 
parts are marked similarly in the three figures. 

Fig. 101. — Sulci — Ro., Rolandic or central; g, its superior genu ; Sy. a, anterior limb of Sylvian 
{x, ascending part, y, horizontal part) ; Sy.p, posterior limb of Sylvian ; Sy. p, asc, ascending ramus 
of posterior limb ; Z^, superior frontal ; /,, inferior frontal ; /,, middle frontal ; Z^, paramesial frontal ; 
d, diagonal, placed in this instance rather low down, and communicating with the Sylvian ; p.o. in/, 
inferior precentraJ ; p, o. i. ant. , its anterior ramus ; p. c. sup, , superior precentral ; p. c. m, mesial precentral ; 
p.e. tr., transverse precentral ; rU;. tr., transverse retro-central ; i.-p, inf^ intra-parietal, pai-s inferior 
(inferior postcentral) ; i.-p, sup,, intraparietal, pars superior (superior postcentral);, s, Jior,, 
intraparietal, pars posterior seu horizontalis ; i,p. post., intraparietal, pars posterior (paroccipital of 
Wilder); i.-p, pr, ase.y an ascending branch of the intraparietal; p.-c^ parieto-occipital ; oeo. ant,, 
anterior occipital ; occ. lat., lateral occipital ; calc, posterior end of calcarine ; ^j, first temporal or 
parallel; t^cuc, its posterior ascending extremity, detached; ^,, second temporal; t^asc, its 
poeterior ascending extremity joined to and apparently continuous wilJi the first temporal. 

Gyri— -Fj, F^, F^, first, second and third (superior, middle, and inferior) frontal; a, posterior part 
of third frontal ; ^, middle part (pars triangularis) ; o, orbital part ; A.F., ascending frontal ; A,P,, 
ascending parietal ; 2\, T^, T,, first, second, and third temporal. 

Fig. 102. — Sulci — Ro,, upper end of Rolandic ; p.c.m,, mesial precentral ; /g, mesial frontal ; 
(f.m.y calloso-marginal ; pr. I., prelimbic (anterior end of calloso-marginal) ; pr. I. asc, an ascending 
branch of the prelimbic ; paracentr.^ paracentral (posterior end of calloso-marginal) ; p.l., post-limbic ; 
ro. rostral; ro. inf.^ inferior rostral ; p^-o.^ parieto-occipital ; calc. ant., stem of calcarine ; calc, post»^ 
posterior part of calcarine ; 1 , 2, 3, 4, places where annectent gyri occur in calcarine and parieto-occipital 
fissures; ^„ third temporal ; coll.. collateral or fourth temporal; h (placed on the fascia dentata) has 
the hippocampal fissure just below it. 

Gyri — F,, marginal part of first frontal; C, callosal (gyrus fornicatus); H, hippocampal; unc., 
its uncus; A, dentate ; T^, fourth temporal (fusiform lobule); T^, fifth temporal or infracalcarine 
(lingual lobule). 

c.Cj corpus callosum ; spl.y its splenium ; ^, its genu ; r, its rostrum ; fo, fornix ; Ji., fimbria. 

Fig. 103. — Sulci — flrh.y orbital (sagittal rami) ;, transverse orbital ; olf., olfactory; t^y ^„ f j, 
first, second, and third temporal; coll., collateral (fourth temporal) ; oalo., calcarine. 

Qyri—Rf gyrus rectus ; T^, T^, T^, T^, first, third, fourth and fifth temporal ; H, hippocampal ; 
s.r.a.y substantia reticularis alba ; unc., uncus. 

rh, chiasma ; s.p.a.y substantia perforata antica ; i.e., tuber cinereum ; m, corpora mamillaria, 
accidentally separated from one another in the preparation ; cr, crusta ; tm^ tegmentum ; spl., splenium 
of callosum. 

Fissure of Sylvius. — The most distinct fissure in the adult brain, and also the 
first one to make its appearance in the development of the embryo, is the fissure of 
Sylvius. This deep and conspicuous fissure is seen at the baae of the brain, opening 
out as the vallecula Sylvii (Broca) on to the anterior perforated space. From this 
origin the fissure passes transversely outwards to the lateral surface of the hemisphere, 
where it presently gives off a short horizontal branch (about 2 centimeters long), 
and a rather longer ascending branch (about 3 centimeters), the fissure being then 
continued nearly horizontally as the posterior limb for a considerable distance (8 or 9 
centimeters) obliquely backwards and upwards in the direction of the parieto- 
occipital fissure, having a slightly curved course. It ends at about the junction of 
the middle and posterior thirds of the lateral surface (midway from superior to 
lateral border), usually by bifurcating, one branch passing obliquely upwards, the 
other backwards and somewhat downwards. If the lips of the Sylvian fissure are 
separated, the island of Keil is seen at the bottom of the sulcus. In section this 
fissure, together with the limiting sulcus of the island, forms a T-shaped figure (fig. 95). 
Its bounding convolutions are folded over the island of Reil, and the upper bounding 
convolutions which belong partly to the parietal, partly to the frontal lobe, form the 
operculum of Burdach. 




The antoiiDr horizontal and anterior BBoending limbs of the fisBure subdivide this opercnlum 
into three unequal parte, an upper or fronto-parietal (pars fronto-parietalis), a middle or 
frontal (pars triangnlaris, "cap" of Broca), and a lower or orbital (pais orbitolU) (fig. 101. 
a, b, e). All these are now often spoken of as opercula. The conTolution bonnding the 
Sylvian fiasure below is also spoken of as the temporal operculum, so that four operoala are 
thus enumerated. Thej are formed in the embryo by the maimer in which the mantle comes 
to oTerlap the central lobe. The temporal and fronto-parietal appear flret, above and below the 
Sylvian fossa of the embryo : the frontal and orbital develope much later. The meeting: of 
the four opercula determines the formation of the three limbs of the Sylvian fissure (6g. lOt). 

The Sylvian flsBUte is nsuall; longer in the left than in the ripbt hemisphere ; the difference 
being due to the greater development of the frontal opercolnm on the left side (fig. IOC) 

Tig. 104. — DuaBAHS 

,A. (Cunningiiam.) 
OTcred part of the Sjlvinn fossa of the embryo, the uiuhadeil 

The part printed black represents iii 
portions rejiresent the different opercnla. 

P.P., fronto-parielal operculum ; T., temporal operculum ; F., frontal operculum (pars triangularis 
of third frontal gyrus) ; 0, orbital operculum ; J'.'i., posterior limb of fissure ; a.n., anterior ascending 
Umb ; a.A., anterior horizontal limb. 

In I, the fronto-parietal and temporal opercnia .ire beginning to grow over the fossa; in II, the 
formaUoD of all (our opercnia is advHnccd, the pars triangularis being well marked, and the anterior 
linib U-shaped. In HI, the para triangularis is onlj slightly developed, and the anterior limb is a V ; 
in IV the pais triangalnris is absent and thi^ anterior limb is simple (l-fonn). 

(localisation of epeeoh centre, Broca). The horizontal and ascending limbs of the anterior 
branch of the Sylvian fissure often arise from a common stem (Y-condition, fig. 101 and Sg. 
106, right aide), the pars triangularis beini^ then less developed than usaal. This part may 
evea not form a distinct opercular projection, in which case tlie anterior limb of the Sylvian 
fiEBwe is undivided (I-oondition). 

The anterior and ascending limbs arose by a common stem from the main fissure (Y form). 
in 32 p. c. of tbe hemispheres examined by Cunningham ; independently (V and U form) in 
ST'5 p. c. ; and as a single limb (I form) in 30 p. c. There are sometimes two secondary 
extensions of the Sylvian fissure on to the orbital lobe (orbital limbs), but these are less deep 
and have not the same morpholi^ical importance as the others. 

The posterior limb about corresponds in the adult to tbe level of the sqnaroons suture, but 
In children younger than fifteen years it is rather above this level. The angle which tbe 
direction of the posterior limb forms with a line perpendicular to the superior border of the 
hemisphere (Sylvian angle), varies considerably, but is more acut« on the whole in the child 
than in the adult (Cimninghani). 

In the brain of some monkeys, the posterior limb of the Sylvian fissure joins (snperflciallj) 
the parallel fissure, which it gradually approaches, and the two are continued as an apparently 


oonjoined fissure almost as far as the upper margin of the hemisphere ; this conjunction is 
sometimes found in the human subject. 

of Solando. — The fissure of Rolando,^ or central sulcus (Huschke) 
(fig. 101, Ro, ; and figs. 105, 107 (monkey) ), extends across the lateral convex surface 
of the hemisphere interrupting the general longitudinal course of the gyri and sulci. 
The parallel convolutions which bound it are named respectively the ascmding 
Jronial and ascending parietal convolution or the central gyri. It begins above, near 
the vertex or highest point of the hemisphere, somewhat behind the middle of 
the great longitudinal fissure, and passes downwards and forwards to end near 
the middle of the fissure of Sylvius, the posterior limb of which it sometimes (but 
rarely) joins. The junction is effected by the medium of a small sulcus, precentral 
transverse sulcus (^g^. 101, 106, jt?. c, tr.), the inferior transverse sulcus of Eberstaller, 
which is usually separated from the lower end of the Rolandic fissure by an annectent 
gyrus joining the two central convolutions. The Rolandic fissure usually reaches 
the superior border of the hemisphere, but sometimes stops short of that line ; it 
often exhibits a hook-like backward inclination at this extremity. As just mentioned, 
it passes obliquely downwards and forwards, but not in a perfectly straight course, 
for it has certain well-marked curves. At about the junction of its upper and middle 
thirds it is generally curved with the concavity forwards ; just below its middle 
third it has a second bend with the concavity backwards, while in the lowest part its 
direction is nearly vertical, with a tendency of the lowermost end to curve backwards. 
The upper curve sometimes forms a very distinct bend (superior genu, fig. 101, //), 
representing a deep bay which is here found in the brain of the anthropoid apes (fig. 
105). The middle part of the fissure is then nearly horizontal. It is very rarely 
interrupted in its course, although on separating its lips it may often be seen that 
there is a tendency to the appearance of an annectent gyrus about the level of the 
superior genu, and it is here that the interruption is liable to occur. The fissure 
of Rolando appears early (end of fifth month), being laid down in two parts, an 
upper shorter, and a lower longer portion (Cunningham). In this double mode of 
origin it resembles the precentral and postcentral sulci. 

The acute angle which the slope of the fissure of Rolando forms with the superior border 
of the hemisphere is known as the Rolandic angle. According to Cunningham it averages 
71'7®. The two Rolandic fissures form therefore when looked at from above, a wide V, open 
forwards and forming an angle of liS°. The length of the fissure is about fths of the 'whole 
length of the hemisphere. It is relatively longer and more curved in the anthropoid apes than 
in man. 

This fissure has once been found duplicated, the two fissures replacing it being separated 
by a gyrus (g. Rolandicus) along their whole length (Griacomini). The condition was present 
in both hemispheres of the same brain. 

Farieto-occipital fissure. — The parieio-oc-cipilal fissure is best marked on the 
mesial surface of the hemisphere, where it appears as a deep cleft (fig. 102, p.-o.), 
extending downwards and a little forwards from the margin of this surface to near 
the posterior extremity of the corpus callosum, where it usually joins the calcarine 
fissure, the two together forming a Y which encloses a wedge-shaped portion of the 
occipital lobe {cuneus). On the convex surface the fissure is continued transvei-sely 
outwards for a variable distance, generally only a few millimeters (ext^rfial 2?art of 
the par ieto-occipiial fissure (fig. 101, jp.-(?.) ). This fissure is herie taken as the division 
between the parietal and occipital lobes. The size of its external portion depends 
(inversely) on the size of the annectent gyrus which curves round its outer extremity 
and connects the parietal with the occipital lobe. In Quadrumana (figs. 105, 107) the 
external portion of this fissure is concealed within a deep transverse cleft {Affenspalte) 

^ Although thus named by Leuret (Anatomie compar6e du systdme nerveux, 1889), from attention 
having been directed to it by Rolando a few years previously, this iissore was noticed and figured by Vicq- 
d'Azyr (Trait4 d'anatomie et de physiologie, 1796). 


which intervenes between the parietal and occipital lobes, the cleft tending obliquely 
backwards, bo that the occipital edge somewhat overlaps the parietal (ocdpital 
operculum). This " Affenspalte " is not represented in the adult human brain, but it 
ia apparently represented by a temporary fissure which is seen in the foetus during the 
fifth and sixth months {external perpendicular fissvre of Bischoff).' The parieto- 
occipital fissure appears about the fourth or fifth month on the mesial surface. It is 
abont on a level with the lambda (see Vol. II., p. 83), or a little in front of the 
level of that spot : more so iu the child than in the adult (Cnnniagham). 

The cBlcarme flivara (Huxley).— This is seen on the mesial surface of the 
hemisphere (fig. 102). It is a deep fissure, extending from near the poeterior 

Pr. L. frontal lobe ; Pat. L., 
Twrietal lobe : Oc. L , occipibJ 
lol>e ; TamD. Sph. L., temporo- 
■I- Bplanoi'lBl lobe ; Sylv. /., BuDre 
of Sylviaa: f.Sg.a.. f.Sy. p., iU 
anterior and postenor limbs ; 
/. JIal.. fisanre of Rolando; 
ir. fr. f, , transverse frontal (pre- 
central) fissure; int. par,/., in- 
tra parietal fiaaure ; par. oe. /., 
psrieta-occipital fissure. 

extremity of the brain. 

where it usually begins in 

a T-shaped fork, in a course curved at first upwards and then downwards, and 

ending below the splenium of ttie corpus callosum. The forked posterior extremity 
near the occipital lobe is sometimes cut off from the rest of the fissure, and appears 
Bs an independent sulcus {sulcus exiremns of Schwalbe). In many Quadrnmana the 
anterior extremity appeara to be continued into the hippocampal fissure, bnt this is 
nsually superficial only, and occurs but rarely in the hnman brain. 

The anterior part of the cftloariue fiasnre ia by far Uie deepest part, aod it is this part 
which iodeDte the posterior horn of the lateral ventricle and forms the calcar avis. A short 
distiuice from its anterior extremity the calcarine receives the internal parieto-occipit*! 
fissure, althouf^h in the depth of the latter fissure there is nsnally a small grjins. pasein;; from 
the apei of the cnneas to tie isthmus of the gjrus fomicatus (opposite 1, fi(r. 102) (rnnro- 
Haibir annrrlritt gyrat). This Bometimea oomes to the surface and shuts off the coDtinnitr 
of the tvro fissures, which otherwise form a Y-shaped figure, the stem of the Y beinir formeil 
by the anterior part of the calcarine, the limbs by the pariet«-ocoipital and posterior part of 
the calcarine respectively. This posterior part of the calcarine Is developed independently of 
the stem, which is a direct repreaentative of one of the total flsHurea of Uie f(et*l hemisphere, 
while the poeterior part of the calcarine Qioifi-riar calrarine of Cunningham) is formed mnclk 
later by two depressions, which ultimately nm together and into the true calcarine. The 
origintj independence of these parts is indicated by the existence of two annectent fryri 
(anl/'rior and piotrriur ruiiri'-litiiivaT) concealed within the posterior part of the calcarine : 
one at ite junction with the stem of the Y. and the other near the hinder end. The placet of 
these annectent gyri are indicated by 2 and 3 in flg. 102. 

The parieto-occipital fissnre is frequently interrupted in its depth by two annectent (ryri. 
One of these is the cnneo-limbio annectent ^yrns already mentjoned (0^. 102, I), Uie other, 
placed higher, may be termed the c«neo-qvadrate anm-ctiat (fig:. 102, at i). 

The parieto-occipital is preceded in the f<£tas by a fissure occupying abont the same situa- 
tion, but this nsually disappears before the permanent fissure malceB its appearance. 

The ooUatoral fiamr« (Huxley). — This is seen on the inferior surface, where 
it lies below and parallel to the anterior part of the calcarine (figs. 1 02, 103, coll.). 
It extends forwards towards the tip of the temporal lobe, but does not reach the 

s.'ipilal Bukui of the ndult brain (see p. 152) repre- 


extremity of the lobe. The middle part of this fissure, which mainly causes the 
projection of the collateral eminence in the lateral ventricle (see p. 125), is formed 
independently of the two extremities. 

The calloso-marginal fissure (Huxley) is an extensive fissure of the mesial 
surface, which begins below the rostrum of the corpus callosum close to the anterior 
perforated space, and sweeping round the genu of the callosum runs parallel to that 
body, separated from it by the gyius fomicatus, as far as a little behind the middle 
of the hemisphere, where it turns obliquely upwards, and ends at the upper margin 
of the hemisphere a short distance behiud the commencement of the fissure of 
Rolando (fig. 102). Both the anterior and the posterior parts of this fissure are deve- 
loped independently of and are often permanently distinct from the middle part. 
The anterior part or pralimhk fissure (fig. 102, pr.-l.) sweeps round the genu of the 
corpus callosum, and when distinct from the middle part passes obliquely upwards 
towards the upper margin of the hemisphere. In any case it usually sends a well- 
marked ascending branch towards the margin (fig. 102, pr. 4, asc.). The posterior 
part of the calloso-marginal (paracentral fissure of Wilder, fig. 102) hooks round the 
inflected end of the fissure of Rolando, and is curved round the paracentral lobule, 
which it bounds behind, below, and in front : the last by an ascending ramus, which 
comes off at the junction of the posterior with the middle part of the calloso- 
marginal fissure. 

The six fissiires which have been described are need by anatomists to map out the surface 
of the brain into regions to which the name of ^ lobes " has, not very appropriately, been 
applied. In all, seven lobes are enumerated, viz., the frontal, parwtalf occipital, temporal, 
and limbic, the inland of Rcil, or central lobe, and the olfactory bulh and tract, or olfactory 
lobe. It must, however, be imderstood that these so-called lobes have by no means an eqnid 
morphological value, nor do they correspond precisely with the functional differentiations 
of the hemisphere which can be made out as the result of experiments on animals, and 
clinical and pathological obsei'vations in man.^ The distinction is further artificial because 
the so-called lobes are in many places not marked off from one another otherwise than by 
imaginary lines. Nevertheless it is found convenient for purposes of anatomical description 
to consider the surface of the brain as thus constituted, and they will accordingly be here 
described in the order in which they have been above enumerated; 

THE FRONTAIj IjOBE. — The fissure of Rolando, passing obliquely down- 
wards from the upper margin of the brain towards the Sylvian fissure, marks off the 
anterior part of the hemisphere — constituting in man nearly one-third of the whole — 
as th^ frontal lobe. This term, however, includes not only the part of the external 
surface which is thus marked off, but the corresponding adjacent part (marginal con- 
volution) of the mesial surface, as far as the calloso-marginal fissure, and also the 
under or orbital surface of this anterior part of the brain. In the description of the 
fissures and convolutions within the lobe, these three surfaces \viil be separately 

Sulci akd Gyri of the External Surface. — The precantral suloui 
(pre-Rolandic sulcus of Broca) (fig. 101^ p.cAnf., p.c.sup. bxmSl p.c.m.) has a direction 
parallel with that of the fissure of Rolando, from which it is separated by 
the ascending frontal gyrus. It is sometimes complete, but more usually is 
subdivided into two or three separate portions by annectent gyri, which connect 
the ascending frontal with the superior and middle frontal respectively ; a third 
annectent gyrus passes below the lower end of the fissure, and unites the ascending 
frontal with the third frontal. The uppermost portion (sidcu^s precentralis mesiali^y 
fig. 101, p.c.m.) cuts the upper border of the hemisphere, and appears on the 
mesial surfibce (fig. 102, p. cm.) often as a well-marked vertical fissure, which 

' Certain of them it is trae, such as the olfactory and the occipital lobe and to a less marked degree 
the temporal lobe, appear to have a localized association with the functions of certain special sense 



occasionally rnns into the calloso-marginal, to which it has sometimes been regarded 
as belonging (Schwalbe ^). The next portion {sulcus preceniralis superior)^ is very 
often continued forwards into the first frontal sulcus (/i, fig. 101). Its middle part is 
opposite the upper genu of the fissure of Rolando. The inferior portion (sulcus 
preceniralis inferior) is by far the best marked. It separates the ascending frontal 
from the third frontal gyrus, and usually gives off a well-marked branch anteriorly 
into the middle frontal gyrus (which may, as in fig. 101, p.cj\ant, be the main 
continuation of the fissure). After giving off this branch the fissure is usually pro* 
longed upwards for some distance, but this is not shown in the brain figured, where 
the superior precentral extends unusually low down. The inferior precentral sulcus is 
often joined to the Sylvian fissure, either directly or through the intermediation 
of the sulcus precentralis transversus (see p. 143), or of the sulcus diagonalis (see 
p. 148), but there is usually, perhaps invariably, an annectent gyrus concealed in 
the depth of the fissure even in these cases. The inferior frontal sulcus sometimes 
appears to spring from the inferior precentral, either near its middle, or, as in the 
brain figured, from its anterior branch, but the two are probably more frequently 
separated by an annectent gyrus which here joins the middle and inferior frontal gyri. 

Two well-marked sagittal sulci (superior and inferior frontul) course over the 
external surface of the frontal lobe in front of the precentral fissure ; they subdivide 
this part of the lobe into three sagittal gyri, superior^ middle and inferior. Besides 
these constant sulci, there are certain others which are less constant in their 
occurrence, and in the extent to which they ai*e developed as connected fissures, viz., 
one running along the middle of the superior frontal gyrus, which we will term from 
its position near the upper border, ihid paramesial sulcus (fig. 101,^4), (s. mssiaUs of 
Cunningham), and one running along the centre of the middle frontal gyrus (sulcus 
frontalis medius of Eberstaller), (fig. 101,^). Both of these are not only inconstant 
in their occurrence, but when present are frequently interrupted, and then appear to 
consist of a series of separate parts, which are often united here and there with the 
other frontal sulci. 

The midfrontal sulcus {s, frontalis medius) usually bifurcates in front, and 
becomes transverse (s, transversus anterior, frcnto-marginal sulcus of Wernicke). 

The superior frontal snlcns {f ) is developed after the inferior, and along with 
the upper part of the precentral, with which it is usually in direct continuity. This 
sulcus is often interrupted by superficial annectent gyri passing obliquely from before 
backwards from the first to the second frontal convolution. Anteriorly, the superior 
frontal often passes into the mid-frontal sulcus (Cunningham). This is the case in 
the brain figured (fig. 101). Posteriorly, its line may be continued by a branch 
from the superior precentral sulcus passing across the ascending frontal gyrus. This 
was also the case in the brain here figured. 

The inferior firontal snlcne (^) usually curves forwards from the middle of the 
inferior precentral sulcus towards the frontal pole of the hemisphere. Several small 
secondary furrows pass from it above and below, and it is sometimes subdivided by 
superficial annectent gyri into three portions. Anteriorly it bifurcates, forming a 
transverge piece, which may develop separately. At the apex of the lobe, in front 
of and sometimes forming part of this fissure, are one or two transverse sulci 
forming the sulcus radiatus and lateral fronto-marginal sulcus of Eberstaller. 

Gyri. — Four convolutions are described upon this surface, three of which run 
antero-posteriorly, while the fourth takes a direction obliquely across the brain, and 
parallel with the fissure of Rolando. The three antero-posterior convolutions are 
termed respectively the superior, middle and inferior, ov first, second, and third frontal 

' Schwalbe has termed it the ''sulcus paracentralis," but this is not to be confounded with the 
fissure to which that name has been given bj Wilder (p. 145). 


gyri. They are eeparated from one another by the upper and lower longitndinal 
frontal sulci, and from the fonrth or ascending frontal gyrus by the precentral 
salcuB, which rrms parallel to the fissure of Rolando. 

The flrrt frontal gyms (f,), which ia much the longest, mns parallel with the 
upper margin of the hemisphere, over which it is continuous with the marginal con- 
volution of the mesial sm-face, the two, in fact, really forming a single convolution to 
which the name first frontal is frequently applied. This convolution reaches the frontal 
pole of the hemisphere in front ; behind it is partly continued into the upper end 
of the precentral or ascending frontal gynis, partly separated from that gyrus by the 
npper end of the precentral sulcus ; below it is marked off from the middle frontal 
by the irregular and somewhat interrupted superior frontal sulcus. It is sometimes 
subdivided by a longitudinally conrsing sulcns (paramesial, s, frontalis mesialis of 
Cnnningliam) into two parts, but less often than the second gyrns. This subdivision 
is rarely found in the brain of the negro. 

The second frontal gTinu {F^) runs below and parallel to the first. lb is 
separated from the precentral by the precentral sulcus, the course of which is, 
however, here usually interrupted by a well-marked annectent gyrus. The inferior 
frontal sulcus separates it from the third gyrus. It is also often subdivided by a 
longitudinally coursing sulcus (mid^ntal sulcus) into two parts, an upper or lower, 
which are sometimes described as distinct convolutions. 

The third frontal gynu {F\), the smallest of the three, is curved around both 
the anterior and the ascending limbs of the Sylvian fissure, which deeply indent the 

Left Bide. Right nide. 

, , . . inf., lower end of inferior precentral, very i 
IS on the right side with, d, diagonal aulcuB (on 
p.c. tr, transverso precentral ; S^.a, anterior limb of Syluian fissure ; x, mniud aaccnucna, tj, ramus 
borizontalis ; o, poMerior part of third frontal (divided bj (he diagonal auleua into two parts, vii., pars 
baailoria behind, and pan aaoendene in front) ; i, middle part of third frontal or para triangularis, 
parti; subdirided on the left side by seoondar; sulci ; e, orbital i«rt of third frontal. 

gyrus, and subdivide it into three parts, anterior (pars orbitalis), middle (pars trian- 
gularis), and poslerior (para basilaris). It is more developed on the left side of the 
brain than on the right — coirespondingly with the loailization of the speech-centre 
on the' left aide (Broca). This increased development chiefly afl'ects the triangular 
middle part which lies between the anterior and ascending limbs of the Sylvian 
fissure (*' cap " of Broca). When well developed, the triangular part entirely separates 
these two limbs (fig. l(iG, left side), when less marked, they are confiuent below (fig. 
106, right side); if the triangular part is absent they are entirely confluent (see also 
fig. 104 and p. 142). This inferior frontal gyrus is connected at its lower and 


posterior end by an annectent gyrus with the lower end of the precentral, while at 
its anterior end it passes round to the orhital surface of the lobe. 

This gyrus is usually regarded as being bounded posteriorly by the inferior 
precentral sulcus, but it is, for many reasons, more convenient to regard the trans* 

veree precentral as the posterior limit. 

It is oooasiojiBUy Bubdirided into two by a Itm^tudinal eoIoub conoentrio with the inferior 
frontal CGiacomini). 

The pars baeiUris is sabdivided tnto two parte (anterior and pocterior diriaiooe) bj an 
oblique fisaore, the fulcui diagonalii at Eberstaller (fl^s. 101 , 106, d). This is nanally diatinct, 
but somotimes joins the inferior precentral (fiR. 106, ri^lit aide), the inferior frontal (fig. 106, 
left aide), or even the Sjlrian fissure. The lait is the case in fig. 101. The pars triangularii 
JB aUo often scored by eecondarj sulci (figs. 101, 106). 

AcoordinK to moat modern anthorities the third frontal gymB is almost or quite rudimentary 
in all primates excepting man. Cunningham points out, however, that although it is true 
that the opercular purt of this conrolntion is not present in the apes, the eame remark does 
not apply to the non-operoular port, and he belieTOs that the inferior frontal sulcne, which is 

■i». (B, A. S.) 

Sulci. - — A.-ip, "Affen- 

Bpalte;" i.-p, intraparieUl ; 

i.-p.>, snperior part of iatra- 

psrietsl 1 -fio., Bolandie ; 

Sy.p, Sjlrias, poateiiorlimb; 
y, , soperior froDtal ; «.r.,ml* 

cm rectus (inferior frnatal) ; 

p. c. I, precentral inferior ; 

p.c.i.a., its anterior nunns ; 

p.e. tr., tiansTene precen- 

trsl ; f , , paralle]. 

regarded by most anthoritlee OS not represented in the apes, is, in fact, represented in them by the 
well-niarked sagittal fnrrow (tu/cm rccttu quadntntanoTum, flg. 107, jt.r.) which tuna forwaids^ 
from near the angle of the inferior precentral salens to tlie apex of the hemiephere. This view, 
which was that taken by Gratiolet (M&noire but lea plis c^r^branx de I'homme et des primates, 
ISGl), civea a well-developed third frontal gyrus to the ape brain, whereas if the snlons in 
question be regarded as the superior frontal (Schwalbe, Miogaxsini), or as the sulcus frontalis 
medius (Eberstaller, Hervf) of the hnnnn brain, the snlcna front^is inferior must be absent 
in the ape, or at most represented by a small fronto-orbital sulcus which is aometimes 
present at the loirermoat limit of the lobe (see fig. 107). Bat the superior frontal snlcoa of 
man is represented in the monkey by one or more deep indentations of the oortez lying in a 
sagittal line near the mai^in and aometimes partly conflnent (fig. 107,/,), and in some apes 
there is also a distinct mid-frontal sulcus besides the saloas rectus : moreover, the atndy of 
the development of tbe inferior frontal snlcnB in man ia also in favour of Qratiolet'a view. 
For a full diBcnaaion of thia qneation the student is referred to Prof. D. J. Canningham's 
memoir, " The Surface Anatomy of the Primate Cerebram," Dublin, 1892. 

The anterior csntral, preoantral, or wwendiag frontal gjmm (&^. 101, 
A.F.) lies between the fissure of Rolando and the precentral sulcus, and extends from 
the superior margin of the hemisphere (where it ia continuous with the posterior 
part of the marginal gyms on the mesial surface) to the Sylvian fissure. It is 
narrowest in the middle, enlarging somewhat above and below. It is usually COD- 
nected, as just mentioned, with each of the three longitudinal frontal convolutions 
by an annectent gyrus, the precentral sulcus being thweby considerably interrupted. 
There is a similar connection by a curved annectent gyrus below the fissure of 
Rolando, with the ascending parietal convolntion. 

Sulci akd Gybi of the Mesial Surface. — On the mesial surface of the 
hemisphere there is only one convolntion which is considered to belong to the frontal 
lobe, viz., the marginal gyrns (fig. 102, F,). This, as above explained, is continuous 
over the upper border with the superior longitudinal of the external surface. It is 
separated from the callosal or fornicate gyrus of the limbic lobe by the calloso-marginal 


fissure, and is partially interrupted by the ascending branches of that fissure. Besides 
these, there is often, but not constantly, a sagittal fissure running along the middle of 
the convolntion. This fissure (sulcus frontalis mesialis s. marginalis) subdivides the 
middle of the gyrus into superior and inferior parts. The antero-inferior part of 
the marginal gyrus is marked by two or three sulci which are curved concentrically 
with the prelimbic part of the calloso-marginal sulcus. These have been termed by 
Eberstaller the rostral sulci (supra-orbital of Broca) (fig. 102, ro,, ro. inf.) Below 
the genu of the callosam the marginal gyrus is continuous with the limbic lobe 
by one or more hrohi frontO'limb'ic annectent gyri. Other annectents are found 
between the several parts of the calloso-marginal sulcus, when this is subdivided ; 
when it is not subdivided they are concealed in its depth. At its posterior end the 
marginal gyrus becomes continuous with the two central gyri on either side of the 
upper extremity of the fissure of Kolando.. But this posterior part of the marginal 
gyrus is nearly cut off from the rest of the gyrus by the anterior ascending part of the 
paracentral salens, and is distinguished as the paracentral or oval lobule (fig. 102). 

Sulci and Otbi of the Orbital Surface. — The orbital bqIcub (H-shaped 
sulcus, triradiate sulcus) is a complex of sulci, which extends over the greater part 
of the flattened orbital surface of the frontal lobe. It consists of a posterior part 
{sulcus orbitalis transversus of Weisbach, fig. 103, o./r), which curves round from near 
the anterior Sylvian fissure laterally, in an arch convex forwards, to end mesially 
near the lateral root of the olfactory tract ; and of three or four sulci having a 
general sagittal direction (sulci orbitaUs sagiitales), and usually communicating 
posteriorly with the transverse orbital. These sagittal sulci vary greatly in their 
number and extent, and in the number and direction of the secondary and tertiary 
sulci, which come off from them, and they frequently produce, with the transverse 
sulcus, the figure of an H, K or X. Weisbach has endeavoured to connect these 
variations with racial and sexual differences, but there does not seem to be any 
foundation for such connexion, and in fact (as is well shown in fig. 103), two 
entirely different types may be found on opposite hemispheres of the same brain. 

Three convolutions are described as lying in front of the transverse orbital 
sulcus, named, according to their position, the inner, middle, and outer orbital 
gyri. The last of these is continuous at the side with the inferior frontal, the first 
and second are the continuations of the superior and middle frontal convolutions. 

On the inner gyrus is seen the olfactory snlcns (s,olf) in which the olfactory 
tract and bulb lie. It has a straight course nearly parallel with the great longitudinal 
fissure, but somewhat inclining towards it. The part of the inner gyrus between 
the olfactory sulcus and the mesial border is sometimes known as the gyrus rectus {R). 
Behind the transverse orbital sulcus, between it and the anterior limiting sulcus of 
the insula, is a fourth gyrus, the posterior orbital, which is also continuous with 
the inferior frontal. 

The continuity of the conyolutions of the external with those of the orbital Borface is often 
mtermpted by a sulcns which crosses their direction, extending: across the front of the lobe 
from the anterior end of the Sylvian (^sulcus fronto-orbitalUf Giacomini ; fronto-marginalig 
lateralis^ Eberstaller). 

FABIETAIi IjOBE. — This lobe lies behind the frontal, in front of the occipital, 
and above the temporal lobe. It is bounded in front by the fissure of Rolando, 
behind by the parieto-occipital and anterior occipital fissures (p. 152), laterally and 
below by the posterior limb of the fissure of Sylvius as far as this preserves its 
horizontal direction, and then by a line connecting this with the lower end of the 
anterior occipital, but it is here freely continuous with the temporal lobe. Above 
and mesially it extends within the great longitudinal fissure and appears on the 
mesial side of the hemisphere, as the quadrate lobule. 

Sulci and Gyri of the Parietal Lobe. — The intraparietal sulcus 


(Tamer) (fig. 101) arches through the parietal lobe, commencing in its anterior 
inferior angle, where it is sometimes, though rarely, continued into the fissure of 
Sylvius. It ascends at first parallel to the fissure of Rolando (pars aseendsns 
inferior s. posicentralis inferior), and then turns backwards horizontally to the back 
of the lobe (pars horizontalie s. posterior), extending nearly to the termination of 
the parieto-occipital fissure, past which it is continued {pars occipitalis, paroecipiUil of 
Wilder) to join the anterior occipital. Its horizontal portion divides the parietal lobe 
into two parts, the superior and inferior parietal lobules, and it is frequently bridged 
across by annectent convolutions connecting those lobules. One or two well-marked 
rami pass into the superior parietal lobule from the upper side of the pars horizon- 
tals, and as many shallow sulci extend from its lower concave side into the inferior 
parietal lobule. 

Above the pars ascendens inferior and ofi^n separated from it by an annectent 
gyrus connecting the superior parietal lobule with the ascending parietal gyrus is a 
short vertical fissure {posicentralis superior), which is termed by Cunningham the 
pars ascendens superior, since in a large number of instances it is directly continuous 
with the pars ascendens inferior (the bridging gyrus being then absent), and the 
two conjoined parts then constitute a sulcus which runs parallel to the fissure of 
Rolando, and is termed the postcentral sulcus (Ecker). 

Although the condition with a detached pars aacendens superior is to be r^^arded as typical 
of this sulcus as shown both by its occurrence in most of the Quadrumana and the course of 
its development in the human embryo, it is by no means the most common in the adult 
human brain, the most usual condition being that here figured (fig. 101) in which there is a 
complete postcentral sulcus from which the horizontal arm passes off backwards at an oblique 
angle towards the occipital lobe, although generally interrupted near the anterior limit of that 
lobe by an annectent gyms. An arrangement of this character was met with by Cunningham 
in 56 p. c. of his cases. In 16 p. c. a more or less complete postcentral sulcus was present, 
and was cut off from the horizontal part of the fisstire by an annectent gyrus. Occasionally 
the postcentral sulcus communicates above, and sometimes also below, with the fissure of 
Rolajido. Three deep annectent gyri partially interrupt the horizontal part of this fissure and 
join the superior and inferior parietal lobules (Eberstaller) ; these have been supposed to be 
a human characteristic, but they occur in the Chimpanzee and occasionally in the Baboon 
(Cunningham). ( 

In rare cases the pars ascendens inferior off this fissure is 'cut off from the pars horizontalis, 
and the latter is continuous with the pars ascendens superior alone. In other and also rare 
instances all the ^arts of the fissure are separated from one another by bridging convolutions, 
so that the fissure appears as four distinct parts, viz., the two portions of the postcentral 
sulcus (lower and upper), the pars horizontalis and the pars occipitalis. 

The occipital continuation of the intraparietal fissure is sometimes separated from the 
rest of the fissure (paroecipital fissure of Wilder). It usually terminates posteriorly by 
joining a sulcus which is nearly vertical to its direction, the svJctut transversus oeeipitalU of 
Ecker (sulcus occipitalis anterior^ fig. 101). This will be further noticed in connection with 
the occipital lobe. In the monkey's brain the occipital termination is concealed within the 
deep cleft (Affenspalte) formed by the occipital operculum. 

Below the postcentral sulcus and cutting into the margin of the f ronto-parietal operoulum, 
is a small oblique sulcus («. retro-centralis transrersus of Eberstaller) (fig. 101, rtc. fr.). This 
sometimes serves to prolong the intraparietal fissure into the fissure of Sylvius. 

The intraparietal fissure is usually developed in the foetus in four segments (Cunningham), 
which appear in the following order, viz., inferior postcentral, horizontal, occipital, and 
superior postcentral. It is better developed, ?>., more continuous and deeper, in apes than in 
man ; but the superior postcentral part is either not developed or is rudimentary in them 
(fig. 107). The so-called horizontal part is not truly horizontal, but has an upward inclination 
which is more marked in the male human brain than in the female. 

The posterior central, postcentral, or ascending parietal convolution 

(fig. 101, A.P,) h'es behind the fissure of Rolando, between this and the postcentral 
sulcus, and parallel to the ascending frontal convolution, with which it is usually 
continuous below the fissure of Eolando. Above, it is connected by a broad annec- 
tent gyrus with the superior parietal convolution, and is continued on to the mesial 
surface by a narrow annectent which unites it with the posterior part of the marginal 
gyrus (paracentral lobule). 


The superior parietal eoiiToliition or superior parietal lobule (fig. 101) 
is fchat part of the parietal lobe which lies above the pars horizontalis of the intra- 
parietal sulcns, and behind the upper part of the last described convolutiony from 
which it is imperfectly separated by the upper part of the postcentral sulcus. Its 
posterior limit is the boundary of the parietal lobe, viz., the parieto-occipital fissure, 
round the extremity of which an annectent convolution connects this lobule with 
the occipital lobe {upper parieto-occipital annectent gyrus). The superior parietal is 
continuous on the mesial surface of the hemisphere with the quadrate lobule. It is 
often deeply cut into by an ascending branch of the intraparietal sulcus. 

The quadrate lobule (precuneus, i^g, 102) is the part of the parietal lobe which 
is seen on the mesial surface of the hemisphere. It is bounded in front b^ the 
posterior limb of the paracentral fissure, and behind by the parieto-occipital fissure, 
and is incompletely separated from the posterior portion of the limbic lobe by the 
postlimbic fissure. Its surface is indented by one or two furrows which cut the 
margin of the hemisphere, and extend a variable distance over the surface of the 
lobule (precuneate sulci). 

The inferior parietal lobule is embraced within the curve of the intraparietal 
Bulcns. It is bounded behind by the lower limb of the anterior occipital fissure. It 
is divided into three gyri, viz. : the supramarginal, the angular, and the postparietal 
(j^g, 101). The supramarginal convolution lies behind and below the anterior 
part of the intraparietal sulcus, beneath the lower end of which it is continuous with 
the ascending parietal convolution. It arches round the upturned extremity of the 
fissure of Sylvius, to become continuous with the superior temporal convolution 
below, and with the angular behind. The angular gyrus, connected in front with 
the supramarginal, bends over the end of the parallel (first temporal) sulcus, and is 
continued below into the first and second temporal gyri. Behind, it is separated 
from the postparietal gyrus by a shallow vertical sulcus, which may be absent. The 
postparietal gyrus curves round the upturned end of the second temporal sulcus. 
(In the brain figured this appears like a continuation of the first temporal sulcus.) 
It is continued below into the second and third temporal gyri. 

OCCIPITAIj IjOBE. — This lobe is very well marked off in Quadrumana by 
the deep cleft (Affenspalte) before mentioned (p. 144) ; but in man the line of 
demarcation between it and the adjacent parietal and temporal lobes is less distinct. 
It is relatively much larger in Quadrumana, especially in the lower monkeys, than 
in man. 

The lobe is of pyramidal shape, lying behind the parietal and temporal lobes. 
In the adult its length, as compared with that of the whole hemisphere, is about as 
21 to 100 (occipital index, Cunningham). It has two free surfaces, an external or 
lateral, and a mesial. It occupies the superior fossa of the occipital bone. On the 
external surface it is bounded in front by the parieto-occipital fissure, by the anterior 
occipital sulcus, and by a line connecting the lower end of this sulcus with the 
posterior extremity of the calcarine fissure. The line in question mainly corresponds 
with a horizontally-directed sulcus, which is termed by Eberstaller the lateral occipital : 
this sulcus may therefore be regarded as the lower boundary of the occipital lobe on 
the lateral surface. On the mesial surface of the hemisphere the lobe is marked off 
by the parieto-occipital fissure from the quadrate lobule, and by the. posterior calcarine 
from the temporal lobe (fig. 102). 

In assigning' the above limits to the occipital lobe I have followed Eberstaller, and have 
departed from the usual description which includes in the lobe all the parts behind the plane 
of the parieto-occipital fissure, and therefore the posterior parts of the parietal and temporal 
lobes as here described. It seems to me, however, that Eberstaller^s definition, although it 
confines the occipital lobe in man to relatively small limits, has the advantage of assigning 
well-marked anatomical boundaries to it and to the adjacent lobes, thus rendering a descrip- 
tion of this part of the brain more easy. 


External Surface. — The bounding sulci of the external surfece of the occipital 
lobe are, as we have seen, the external part of the parieto-occipital, the anterior 
occipital, and the lateral occipital. The parietooccipital has already been described 
(p. 148). The anterior occipital aulciui (traasTerse occipital of Ecker) is a 
transverse furrow, which is laid down as a distinct sulcus in the foetus, but is later 
almost invariably joined by the horizontal part of the intraparietal, of which it 
then appears to be the bifurcated posterior end (p. 160). In Quadrumana it is 
concealed by the occipital operculum, but on drawing this aside it may still be seen 
at the bottom of the " Affenspalte." It approaches the mesial border of the hemi- 
sphere above, behind the parieto-occipital fissure, from which it is separated by an 
annectent gyrus which joins the occipital lobe with the superior parietal lobule. 
Its lower end, which is often curved forwards, is usually separated from the lateral 
occipital by the inferior parieto-occipital annectent gyrus uniting the occipital 
lobe with the postparietal gyrus. In the brain figured (fig. 101), this second 
occipito-parietal annectent lies deeply, and the two fissures are superficiallT 

The lateral occipital sulcus runs somewhat obliquely upwards and back- 
wards from a short distance below and in front of the lower end of the anterior 
occipital towards the occipital pole of the hemisphere. But before reaching the 
pole it generally bifurcates in a Y, one branch curving upwards into the occipital 
lobe, the other downwards towards the posterior end of the calcarine ; it may be 
embraced by the bifid extremity of the latter. Around its end a lateral occipiio- 
temporal a7inecient gyrus curves, uniting the occipital lobe with the third temporal 
gyrus. Within the limits of the occipital lobe as here defined there are usually two 
or three small sulci of varying extent. These are, however, not constant enough in 
position and direction to serve for marking out this surface into distinct gyri. 

The external surface has usually been described (je.g.^ in previouB editions of this work) as* 
havinpT three gfTri, a superior, middle and inferior. But this description does certainly not hold 
good for most brains, and if any division is to be made it must be into anterior (between the 
Anterior occipital sulcus and the upturned end of the lateral occipital) and posterior (behind 
the upturned end of the lateral occipital). 

Mesial Surface. — The mesial surface of the occipital lobe is occupied by a 
well-marked gyrus termed the cnneate lobule (cuneus) (fig. 102). This is of u 
triangular shape, and is bounded in front by the parieto-occipital fissure, and below 
by the calcarine, while above and behind it reaches the margin of the hemisphere 
and is continuous with the external surface. It is indented by two or three shallow 
vertical sulci. 

The parieto-occipital and calcarine fissures which bound the mesial surface have 
already been described, as well as the deep annectent gyri which pass across them 
and connect the cuneus with the adjacent lobes (see p. 144). 

The superior longitudinal venous sinus in passing downwards causes an impression on the 
inner side of the occipital pole of the hemisphere (Bastlan). This impression is generaUy 
found on the right side, but sometimes on the left. 

According to the usual description, which has been followed in previous editions of this 
work, the occipital lobe has a tentorial surface, comprising the lingual gyrus and posterior 
part of the occipito-temporal gyrus (fusiform lobule), which run in a sagittal direction, and 
are separated from one another by the posterior end of the collateral fissure. But by confining 
the occipital lobe to the limits above assigned, these gyri and sulci become entirely included 
in the temporal lobe, along with which they will accordingly be described. 

TEMPOBAL IiOBE. — The temporal or temporo-spJienoidal lobe is bounded 
above for two-thirds of its length at first by the stem and afterwards by the 
posterior limb of the fissure of Sylvius, which separates it from the frontal and part 


of the pariefcal. Behind and above it is continuous with part of the parietal lobe. 
Behind^ it is separated from the occipital lobe by the lateral occipital sulcus. It is 
somewhat pyramidal in shape, haviug three surfaces, viz., lateral, superior and 
inferior, the superior, concealed within the fissure of Sylvius. The under surface 
adjoins the limbic lobe, being separated from the hippocampal gyrus of that lobe by 
the collateral fissure. The rounded apex of the pyramid is free, is directed forwards, 
and lies underneath the orbital surface of the frontal lobe, from which it is separated 
by the broad commencement of the Sylvian fissure. 

Gyri and Sulci op the Upper Surface. — The upper surface of this lobe, 
directed towards the insula and fronto-parietal operculum, is marked by two or three 
transverse temporal gyri (Heschl). On the nearly smooth part of the surface in 
front of these are three short gyri (m, fig. 108) separated by shallow sulci, which are 
directed from the gyrus longus insulse towards the tip of the temporal lobe. 

Sulci and Gyri of the Lateral and Under Surfaces. — On these surfaces 
there are four sulci with an antero-posterior direction. The first or superior 
temporal sulcus, also termed from itfi relation to the Sylvian fissure the parallel 
fissure (fig. 101, ^), is an important furrow, appearing in the sixth month, and being 
constant in the Primates. In many monkeys it is more extensive than in man. 
nearly reaching the parieto-occipital fissure at the margin of the hemisphere. The 
angular gyrus curves round its extremity. Both this and the second temporal turn 
upwards as they poss back. The upturned extremity of the second sulcus may 
appear as a continuation of the parallel, as in the brain here figured (fig. 101). The 
fissure is sometimes interrupted by a small gyrus connecting the convolutions above 
and below it. The second temporal sulcus (/.j) runs parallel to and below the 
last, but is less constant in extent and direction. It is often interrupted by one or 
more vertical connecting gyri. The postparietal gyrus curves round its extremity. 
The third temporal sulcus (t^) is seen on the under surface of the lobe, extending 
behind nearly to the occipital pole. It is often interrupted near its anterior and 
posterior ends, and sometimes also about the middle by annectent gyri. In front it 
generally fails to reach the extremity of the lobe, which forms a smooth " pole " from 
which most of the sulci diverge. A fourth temporal sulcus (^4) is formed by 
the collateral fissure, which has already been noticed (p. 145) (figs. 101, 103). 

On the lateral surface of the lobe three convolutions can usually be distinguished. 
The first or superior temporal gsrrus (fig. 101, Fy) bounds the posterior limb of 
the Sylvian fissure below, and is continuous behind with the supramarginal and to a 
less extent with the angular convolution of the parietal lobe. The second temporal 
gyrus (^3) is continuous with the angular and postparietal gyri. The tliird 
temporal gsrrus {T^) is continuous with the occipital lobe by the annectent gyrus 
which passes between the calcarine and lateral occipital sulci. On the under surface 
of the lobe is the fourth temporal gyrus, lying between the third temporal 
sulcus and the collateral fissure. The second and third gyri are convolutions of 
gome thickness, and are a good deal interrupted by transverse and oblique secondary 
sulci. The fourth, which was formerly known as the first occipito-temporal, is 
narrower, and more sharply marked off by its bounding sulci. Its posterior part, 
which has been termed the fusiform lobule, is usually described as belonging to the 
occipital lobe (see previous page). Lastly, between the posterior part of the collateral 
and the calcarine fissure is a fifth .temporal gjxvLu, which was termed by Huschke 
the lingual lobule, but it is better termed infracalcarine gyrus {subcalcarine gyrus of 
Wilder). This is continuous in front with the hippocampal g3rros of the limbic 
lobe (see below). It is joined by two deep annectent gyri, which pass across the 
posterior calcarine fissure, connecting this gyrus with the cuneus (fig. 102, 2 and 8). 

The temporal lobe lies in the middle fossa of the skull, and its posterior part 
overlies the tentorium. 


THE OSTNTRAXi IjOBE OB IBUUTD OP BZIL. — This lobe U entirely 
concealed in the adult human brain within the fiesure of Sylvius, the margins of 
which form opercula (see p. 142} which overlap the lobe. The central lobe cone- 
Bponds with the corpus striatum on the interior of the hemisphere (fig. 88), and 
probably in consequence of its close connection with this mass of grey matter, which 
appears early as a thickening of the lateral wall of the vesicle of the cerebral hemi- 
sphere (vide Embryology, Vol. I., p. 69), this particular part of the hemisphere does 
not keep pace with the general expansion which the hemiBphere-Tesiclea nndergo, 
and hence in consequence of that eitpansion it becomes overlapped and concealed by 
the rest of the hemisphere. On acconnt of this early fixation and the close topo- 
graphical relation between it and the largest of the basal ganglia, the central lobe 
(along with the baeal ganglia and the continuation of the peduncles between them) 
is freqnentlj spoken of as the stem (German, SI(Wimt/ieil) of the hemisphere, the 
remainder of the cerebnun, which covers it in, being known collectively as the manUt. 

To see the island it is necessary to cut away the opercnla (fig. 108). It then 
appears as a triangular anrface somewhat bulged outwards, the base of the triangle 

t.e., Eulcni ccntnlii ibsiiIb ; 
' 1> 2, 3, gjri brsTw : 4, 5, gjnu 

longiu; ii.B.a., f.H.'i., M-fLv., 
anterior, Buperior, nnd poatenor 
limitiDg sulci ; I, limeD inmla ; 
F, arbilal ptul of third frontal 
gjTiu; 7',, ?',, Gut and aecood 
tempDca] gyri ; x.y, upper tnU' 
verae temporal gjrj ; g. tr. i. . gym* 
transTenuB insulae, paatiag at a, 
into the orbital pait of the thii^l 
frontal ; b. cannecCioa of gyro* 
longm ioBuIn with apex of tem- 
poral lobe ; 111, short g;ri on the 
uppor anrface of the tempoial pole. 

being directed upwards and the apex being at the vallecula Sylvii. -This surface ia 
marked out by shallow sulci, which have a fan-like arrangement converging from the 
base, towards the apex of the triangle, into several straight gyri having a similar con- 
vei^nt course. One of these sulci, which is deeper and appears earlier than the rest, 
and is also more constant in lower Primates, has been termed the auloiu o*ntn)ia 
fwMiT— (Guldberg) (fig. 108, s.c), and this serres to subdivide the lobe into two 
parts, apreeenlral and postcentral lobule. Since the line of direction of this snlcns 
nearly corresponds with that of the fissure of Rolando in the mantle, the pre- and 
posl>central parts of the island similarly correspond to the &ontal and parieto- 
temporal lobes of the mantle ; and they are in fact in continuity with the parts 
of those lobes which form the opercula. The island is, however, separated from 
these adjacent parts by a sulcus (btiIoiu limitMW iim]») which almost entirely 
Eurronnds it, and which is itself formed of an anterior, a superior, and a posterior 
part (fig. 108). The anterior and posterior parts of the limiting sulcus are, 
however, deficient near the apex of the lobe, so that there here occurs a direct 
continuity (by a small convolution, the gyrui tratuvertua inaula of Eberstaller) 
between the orbital part of the third frontal convolution as it dips ronud the margin 
of the Sylvian fossa, and the precentral lobule on the one hand, and between the 
limbic lobe and the extremity of the postcentral lobule on the other hand. 


The preo«ntral lobule of the insala is formed of a few short oonvolutionB ^gyri hrevei) 
(fig. 108, 1 , 2, 3) oonverging from the base of the triangle but falling short of the apex of the lobule, 
which is smooth and forms a slight prominence (pole of the island^ p). These convergent gyri 
are usually three in number (anterior, middle, and posterior), being subdivided in this manner 
by secondary and somewhat shallow sulci, having the same direction. The most marked of 
these sulci lies between the middle and posterior gyri breves, and has been named tulctis pre' 
centralis ineuUe. A fourth small gyrus is described by Eberstaller as lying deeply underneath 
the orbital operculum. This he has termed the gyrus hrevU accessoriue. This accessory gyrus, 
and usually also the anterior of the three gyri breves, look forwards, lying upon an anterior 
surface of the insula, which is sometimes nearly at a right angle with the lateral or general 
surface, in other brains hardly marked off from it. Its grey matter is continued over the 
anterior limiting sulcus into that of the orbital gyrus. The grey matter of the rest of the 
precentral lobule is continuous superiorly with that of the frontal lobe, inferiorly with that 
of the anterior perforated space. The inferior transitional part has been termed the threshold 
of the island {livien insula, Schwalbe). 

The postcentral lobule {gyrus Ungus insula' of Giacomini (fig. 108, 4, 6) ) is also often 
subdivided at its upper end by a longitudinal furrow (jmlcus postcentralis insula) into two parts, 
anterior and posterior. Its grey matter is continuous below with the tip of the hippocampal 
gyrus, laterally with that of the first temporal gyrus, above and posteriorly over the limiting 
sulci with the grey matter of the parietal and temporal opercula. 

The three principal furrows of the insula (sulcus centralis, s. precentraUs, and s. post- 
centralis insulsB), which radiate from the vallecula Sylvii, have been compared with the three 
similarly radiating fissures of the mantle, viz., the fissure of Bolando, the precentral fissure, 
and the intraparietal fissure. They are not, however, directly continuous with those, being 
arrested at the sulcus limitans insulse. Sometimes the fissure of Bolando is continued by a 
small sulcus (transverse precentral) almost into the s. centralis insulae. Below and anteriorly 
the sulcus centralis insul» comes into close relationship with the extremity of the calloao- 
marginal sulcus. 

JiJBCBIC IiOBE. — The callosal gyruSy with its contiiination the hippocampal 
gyruBy were separated by Broca, on morphological grounds, from the other parts 
of the hemisphere, as a distinct lobe, intimately united in front and below 
Avith the olfactory lobe ; and the name of grands lohe limhiqm was given by 
him to these combined lobes. To this lobe of Broca, Schwalbe added the other 
central parts of the mesial wall of the hemisphere, viz., the lamina sepii lucidi and 
the dentate convolulionj as well as the fornix ; looking upon these as representing 
an inner encircling convolution concentric with the gyrus fomicatus and uncinatus, 
and naming the whole lobe thus reconstituted, the " falciform lobe," the olfactory 
lobe being, however, excluded. 

To the parts included by Schwalbe there must now be added a rudimentary 
supracalloml gyrus (represented in man principally by the longitudinal strisB ojf 
the corpus callosum), which is continuous with the dentate convolution posteriorly, 
and with the rudimentary gyrus geniculi (see p. 158) anteriorly. The lobe must 
further include the peduncles of the corpus callosum (see p. 127), which appear to 
represent a rudimentary gyrus (gyrus subcallosus, Zuckerkandl), and also another 
rudimentary gyrus underneath the corpus callosum, partly imbedded in and 
intimately connected with the fornix, to which the name of gyrus infracallosus or 
gyrus fomicis may be applied. 

As thus constituted the limbic lobe is bounded circumferentially mainly by two 
important fissures, the calloso-marginal above, and the anterior part of the collateral 
below, while the less constant postlimbic sulcus separates it behind from the 
parietal lobule, and the anterior end of the calcarine cuts into it just below the 

The circumferential boundary is least distinct opposite the qiuidrate lobule, from which it 
is only separated by the small postlimbic sulcus, which in man is only occasionally continued 
into the calloso-marginal. But in many animals the fissure which forms the external boundary 
is uninterrupted or nearly so, and forms the limhio fissure of Broca. This might perhaps 
more appropriately be termed the outer limbic fismre, since the calloeial sulcus and the 
hippocampal fissure form together a second crescentic fissure within the limbic lobe, which 
may be distiuguished as the inner limUc fissure. The internal limit of the lobe is formed by 
the fissura choroldea (Schwalbe), through which the choroid plexus is invaginated into tho 


lateral ventricle. The lobe u pierced b; Uie great commuaiire of the hemjxpherea (tJie coipUB 
cAllotum} and also bj the anterior oominifaiire. It ifl connected bj annectent ^yri wiUi the 
lingrual gyrui at the temporal lobe (eee p. 153), with the coneus of the occipital lobe (bj a 


gji^' hidden within the internal parleto- occipital fiaanre), with the qaadAt« lobule, with the 
orbital part of the frontal lobe, with the anterior part of the temporal lobe, and with the post- 
central lobols of ihe insula. 

Each end of this crescentio lobe is oonnected with one of the roots of the olfactory tract. 
viz., the commencement of the Kyias fomicatua with the mesial root and the termination of 
the hippocampal Kf ms with the lateral root 


o»tiU| gyru eiaguli, '"^"'"r*^ gyrum. This is an extenBive convolution which 
liea between the mai^inal gjnis of the frontal lobe and the quadrate lobule of the 
parietal lobe above and the corpus callosam below. The convolution sweeps round 
the Gorpns callosnm, beginuing below its roiitrnm, where it abuts on the subcallosal 
gjrne, and ending a little below the level of the aplenium by becoming coutinnona 
with the posterior end of the hippocampal gyrus. Where it passes into that gyms 
it is much narrowed (igthmuB).^ It ia separated from the corpus callosum bjr a fissure 
which 18 termed the callosal sulcus. 

Thb bippooampal gyma (subicutvm comu ammonis), also known, together 
mth the infi'acalcarine, as the naoiiutte gynuii is continued from the isthmus of 
the callosal convolution, and passes forwards above the anterior part of the collBteral 
fissure towards the apex of the temporal lobe (figs. 102, 103). It ends before 
reaching thia, however, becoming considerably thickened, and forming a recurved 
projection which looks backwards and inwards, and is known aa the uticus. The 
hippocampal gyrus is covered superficially by a well-marked reticular layer of white 
fibm (^substantia reticularis alba, Arnold (fig. 103, s.r.a.) ). 

The dantftts gjnm (/aseia dentaia Tarini {6g. 102, fig. 110,/.rf.)) lies above the 
hippocampal gyru8,f rem which it is separated by the hippocampal or denlaUJissure {f.h). 

* Bj tome KuthoiB tbe term gjruB fomicatuB is maile to include Ibe hippocampal pnw. 


It is a narrow conTolation having a pecniiai'ly toothed or notched appearance at its free 
border, hence the name dentate. Above and overlapping it is the fimbria, from which 
it is separated Bnperficially bj a shallow sulcus (fimbrio-dmfate,f.f.-d), narrow in front 

fig. 110.— DiAanAU Of X. SEonoH iHRocaH TBI LErr HiprooAVPAL Bidion (E. A. S.) 
J.O., baiia cerebri ; tr., traotna optical ; B. o., naclena CAarUtm ; /, ch., fiaanra chonrideft ; Jf., 
fimbria ; f.f.-d., Graara Gmbrie-deatAta ; /. d., fascia dentata, /. A., fisann hippocampi ; A, bippo- 

hippocampi ; m,, its medullaij c«iiln 

bnt broadening oat behind, where it formB 
a triangnlar depression below the splenium 
of the callofium. The gyrasdentatns begins 
pilsferiorly just behind and above the 
splenimn by a fiDe carved lamiaa (fasciola 
cinerea), which is contianons with the 
long}tudinal atriee (both lateral and mesial) 
of the- GorpOB callosnm (p. 127). From 
here it bends downwards, lying along the 
isthmns of the gyrus fornicatus and then 
along the npper border of the hippocampal 
gyrus ; here the posterior pillar of the 

fornix passes to its upper border in continuity with the fimbria (see p. ISO). An- 
teriorly it is contiaaed into the cleft between the hippocampal gyrus and its uncus, 
where it becomes lost to view. But if this cleft be opened oat (fig. Ill) the dentate 
gyms is seen to exhibit a sharp curve within it, and in continuity with the curved 
end a greyish band emerges from the cleft and passes transversely over the uncus 
to disappear on the ventricular surface of that gyrus (LuBchka, Giacomini). 


and secondarily convolnted gyras dentatns which covers the under surface of the splenium in 
some mammals (G. Retzius). 

Hidden beneath the posterior part of the callosal gryrus, between this and the subsplenial 
X)art of the gyrus dentatus, a small projection of the cortex is usually to be found, about 1 cm. 
long and 2 mm. to i mm. broad, marked by 1 to 4 semicircular eminences. This has been described 
(by A. Retzius origiually, and more recently and fully by Zuckerkandl) under the somewhat 
misleading name of callosal gyrus (Balkenwindung), but is not to be confounded with the 
gyrus cinguli which has long been so denominated. It is best developed in osmatic mammal8>. 

The fimbria (fig. 102,^) represents the white matter of the hemisphere, which 
here comes to the surface along the si^e of the dentate gyrus. It is continuons 
with the alveus which covers the hippocampus major within the lateral ventricle, 
and this is continuous with and forms part of the central white matter. The 
fimbria itself, however, appears to be actually formed of fibres which are prolonged 
into it posteriorly from the pillars of the fornix : anteriorly it is continued into the 
white matter of the uncus. In section the fimbria appears as a somewhat club- 
shaped expansion of the alveus, exhibiting a hook-like mesial prolongation (fig. 110,/). 
This is the section of a thin lamina {tcBnia fimbricB), continuous with the epithelium 
covering the choroid plexuses which here invaginate the ventricular epithelium. 

The only sulcus within the limbic lobe which remains to be described (the 
callosal sulcus and the fimhrio-deniate sulcus having been already noticed) is the 
Mppocampal or dentate fissure (fig. 102, h). This begins as a shallow furrow 
just above the posterior end of the splenium corporis callosi, between the fiwciola 
cinerea and the end of the gyrus fornicatus, it then lies between the remainder of 
the dentate gyrus above and the isthmus gyri fornicati and hippocampal gyrus below, 
and becoming deeper as it passes forwards ends in the bend between the hippocampal 
gyrus and its uncus. This fissure causes the elevation of the hippocampus major 
or cornu Ammonis in the descending horn of the lateral ventricle (fig. 110). 

Gyms fomloU. — The fornix which has already been in the main described (p. 129) also 
belongs to the limbic lobe as here defined. It contains an association-bundle uniting the 
hippocampus major with the olfactory lobe. This bundle, the olfactar^ bundle of the cornu 
Ammonis (Zuckerkandl), best developed in osmatic mammals, is contained within the body of 
the fornix, but leaves the anterior pillar to pass in front of the anterior commissure and then 
to run in the subcallosal gyrus to the vallecula Sylvii. Here it divides into two parts, one 
(pars olf actoria) passing by the anterior circumference of the lamina perforata anterior to the 
inner root of the olfactory tract, and the other (pars temporalis) at the hinder border of the 
anterior perforated lamina to the point of the hippocampal gyrus. This is the band which has 
been described (by F. Arnold and Broca) as continuing the peduncle of the corpus callosum 
with the hippocampal gyrus. 

In the monkey there is a band of grey matter running along the upper surface of the 
fornix, on each side near the middle line, wedged in between it and the corpus callosum. 
This closely resembles the supracaDosal gyrus above the callosum (see below), and appears to 
be part of another rudimentary gyrus which may be termed ffj/nts infraealUtsus, or, including 
certain patches of grey matter which occur here and there in the substance of the fornix. 
gyms fornivis. 

The cinsrultun, which also belongs to the limbic lobe, is a tract of association-fibres run- 
ning in the gyrus hippocampus and gyrus fornicatus. The bundle has for the most ypfnt a 
longitudinal course within the white matter of these gfyri ; but the fibres probably commence 
in the cortex, and since they constantly tend, as the whole bundle courses longitudinally, to 
diverge into the adjacent white matter of the hemisphere, it appears probable that they 
connect the hippocampal and callosal gyri with the cortex of the outer surface of the hemi- 
sphere (Beevor). A bundle of fibres having a somewhat similar course in the anterior 
descending part of the gyrus fornicatus is usually described as part of this tract ; but according 
to Beevor it is doubtful if these fibres can be considered to belong to the ciugulum ; at all 
events, their continuity with the remainder of that tract could not be traced. 

OtyTMM limbicus. — The longitudinal strisB of the corpus callosum (p. 127) belong to a thin 
lamina of grey matter which extends over the surface of the corpus callosum from the lower 
edge of the gyi'us fornicatus, and is much better developed in osmatic mammals than in Primates 
(Valentin, Jastrowitz). The striae, together with this grey matter, repra«*ent a degenerated con- 
volution {supracallosal gyrus, Zuckerkandl), which is continuous posteriorly with the fasciola 
cinerea, t;c., with the dentate gyrus. Together with another degenerated gyrus in front, which is 
represented only by the prolongation of the stria medialis (gyms geniculi of Zuckerkandl) these 


f onn a radimentary gyras (bordering gyrrts, gyrut marginalU,^ Germ. Handwitidujig), which is 
oarved aroand the brain-stem and the oentral parts of the hemisphere, lying within and conoen- 
trio with the larger and well-developed gyros formed by the fornicate and hippocampal gyri. 
The lamina of the septnm Incidam, and the so-called pednnde of the corpos callosnm (gyms 
sabcalloBus of ZnckerkaDdl) also belong to this bordering gyrus, but have become separated 
from the snpracallosal part by the development of the corpus callosum ; and the gyrus 
iniracallosns (where this exists) and the fornix and fimbria may also be considered to form 
part of it.' 

OIiFACTOBT IiOBE. — This lobe (fig. 112) lies at the ventral aspect of the 
frontal lobe. It is nidimentarj in man and other Primates, and in the seals, and is 
lacking in Cetacea, bat in all other mammals (osmatic mammals, Broca), and in 
vertebrates generally, it is well developed and forms a distinct portion of the cerebral 
hemisphere, enclosing an extension of the ventricular cavitj. In some mammals 
(«.^., horse) this extension remains throughout life in free communication with the 
anterior horn of the lateral ventricle, in others {e.ff.^ dog) the communication is lost. 
In the human foetus of from two to four months, it appears as a hollow projection 
of the fore-brain, but as the walls of this projection thicken by the development 
of nervous tissue within them, the cavity becomes gradually obliterated, and is 
ultimately entirely occupied by a mass of neuroglia (central neuroglia of the olfactory 
tract and bulb). Compare Vol. I., pp. 71 and 79. 

Anteriorly the olfactory lobe is connected with the olfactory cells of the olfactory 
mucous membrane, posteriorly it is connected with the two extremities of the limbic 

The olfactory lobe may be described (His) as composed of two parts or lobules, 
an anterior and a posterior. The anterior olfactory lobuls comprises (1) the olfactory 
bulby which rests on the cribriform plate of the ethmoid bone, and receives the fibres 
of the olfactory nerves, which originate in the cells of the olfactory mucous 
membrane, (2) the olfactory tract, which lies in the olfactory sulcus of the frontal 
lobe, and posteriorly bifurcates into two roots, mesial and lateral, which diverge 
as they pass backwards and enclose (8) a space, the trigonum olfaclorium, which is 
also known as the middle or grey root of the tract, (4) the area of Broca (His), a 
portion of grey matter lying between the mesial root and the peduncle of the 
corpus callosum, and continuous with the commencement of the callosal gyrus. 
This area is separated from the posterior part of the gyrus rectus of the frontal lobe 
by an oblique sulcus (flssura eerotina, His). 

The posterior olfactory lobule is marked off from the anterior by a curved fissure 
{fisBura primay His). It is formed by the portion of brain cortex, which 
appeal's on the surface at the anterior perforated space, and is bounded mesially 
by the peduncle of the callosum (gyrus subcallosus of Zuckerkandl), anteriorly by the 
fissure just referred to, whilst laterally it is continued into the vallecula Sylvii, 
and is concealed by the temporal lobe which overlaps it. The continuation of the 
lateral root of the olfactory tract courses lateral wards and backwards over the surface, 
as it passes towards the anterior end of the hippocampal gyrus. 

The olfMStory bulb (figs. 103, 112) is oval in shape and of a reddish-grey 
colour when viewed from the ventral aspect. It is nearly a centimeter long and 
about a third of this in width ; from its posterior extremity the olfactory tract 
emerges. Its dorsal surface, which is in contact with the frontal lobe, is white and 
is directly prolonged into the tract. This surface presents a longitudiaal ridge 
which fits into the anterior end of the sulcus olfactorius of the frontal lobe. 

The olfkotory tract, sometimes erroneously spoken of as the olfactory nerve, is 
a band of white matter, fiattened on the ventral aspect but ridged along the dorsal 

^ Not to be confounded with the gyms marginalis on the mesial surface of the frontal lobe (see p. 148). 

* Zuckerkandl describes two bordering gyri, an outer and inner, the outer being formed by the dentate 
gyrus, the gyrus supracallosus and the gyrus geniculi, and continued into the inner root of the olfactory 
tract ; the inner by the fimbria, fornix, lamina septi lucidi, and gyrus subcallosus. 


aspect (where it fits into the olfactorj snlcua), and therefore triangalar in section. 
It measures about 2 centimeterB in length and 2J miUimeters in breadth, being 
narrowest anteriorly where it passes out of the bulb, and broadening poateriorly as it 
bifurcates to form the roots. As ah-eady stated it encloses a central grey substance 
formed of neuroglia. 

The trigoniua olfiustorinm and the orsa of Brooa are in fact parts of one 
and the same area of grey matter which forms the base of the anterior olfactory 
lobule, and la traversed by the roots of the olfactory tract. This area is separated 
from the peduncle of the callosum and the posterior olfactory iobule by the fisaura 
prima, and the mesial root of the olfactory tract in passing over its ventral surface 
subdivides it superficially into its two parts. Of these the area of Broca receives 
many fibres from the mesial root as this passes over the surface, whilst the trigonnm 
olfactorium receives others which are directly prolonged into it from the posterior 

Bu, alfactorj bulb ; T, tnut; Tr.o., 
trigone ; R, rMtram of corpiu caltoiain ; 
p, peduncle of corpoa calliWDRi, pauing 
into, g.t, gynu subcalloso* (dugon*! 
tract, Broca) ; Br, Broca's area ; P.p. 
fisaura prima ; F.i, ita\ira, Berotiak ; Co. 
poeilioD of anterior camminare ; L.t, 
luninb teTminalis ; Ch, optic chisuna : 
T.o, optic tiact ; p.olf, pOEterior olfactorj 
lobule (or aaterior perforated *pacii] : 
in,T, mMi^ root; l.r, lateral root of 

end of the tract, and which some- 
times form a distinct middle root 
of the tract. The nltimate des- 
tination of these fibres which pass 
into the trigone is not accurately 
known, but some appear to join 
the anterior commissure and to 
be conducted by this into the 
posterior part of the temporal 
lobe, and others, according to Meynert, may pass across in this commissure to the 
temporal lobe and hippocampal region of the opposite side, an " olfactory chiasma " 
being thereby produced. The evidence in favour of this crossed connexion is, 
however, at present insufficient. Fibres from the posterior end of the olfactorj 
tract also pass directly into the white matter of the frontal lobe : these have been 
named the upper or dorsal root of the olfactory tract (Henle). 

The outer or lalercU root passes as already stated over the outer part of the 
substantia perforata anterior, and becomes lost to view in the depth of the vallecula 
Sjlvii. In osmatic mammals it can be traced without difficulty into connection 
with the anterior part of the hippocampal gyrus, and, according to Lnys, with 
the nucleus amygdalae. The inner or mesial root is recurved sharply around the 
posterior limit of Broca's area, and its fibres pass partly into this, partly into the 
callosal gyrus. The olfactory tract has thus a relation to the limbic lobe which has 
been compared to that of the handle of a tennis-racquet to the ring of the blade, the 
two extremities of the curved limbic lobe being continuous respectively with the inner 
and outer roots of the olfcctory tract (fig. 109). The combined olfactory and limbic 
lobes may be spoken of collectively as the rhinejuxphalon ; it is marked off from the 
rest of the hemisphere by the combined calloso-marginal, postlimbic and collateral 
fissures forming together the limbic fissure, and in its development it varies directly 
with that of the olfactory organ. This co-relation in development applies more 


especially to the hippocampal convolntion, which in many smooth-brained osmatic 
mammals forms a considerable proportion of the hemisphere (lobus hippocampi). 

The term rhinencephalon is limited by Tamer to the olfactory and hippocampal lobes, bnt 
there seems no sufficient reason for excluding the remainder of the limbic lobe, the several parts 
of which are all closely inter-related. At the same time it must be pointed out that the 
limbic lobe unqnestionably subserves other functions beside that of a central organ for the 
olfactory sense, since it is present even in those mammals (Delphinidse) which are devoid of 
an olfactory sense, and in which the olfactory lobe proper is entirely absent. The results of 
experiment seem to indicate an association of parts of the limbic lobe with the perception of 
tactile sensations. (Consult on the comparative development of the rhinencephalon and the 
mantle in mammals, "■ The Convolutions of the Brain, a Study in Comparative Anatomy," 
by Professor Sir W. Turner, Journal of Anatomy y October, 1890.) 


Very considerable yariations are found in the course and relative development of the 
fissures and convolutions, and this not only in different individuals, but also on opposite sides 
of the same brain. Even the principal fissures, under which term may be included both those 
which occur as complete folds of the hemisphere-wall (Sylvian, hippocampal, calcarine, 
parieto-occipital, and collateral), and those which are the first to make their appearance (about 
the sixth month of foetal life) as indentations of the smooth surface of the mantle (precentral, 
Rolandic, intraparietal, parallel, olfactory, calloso-marginal), are very subject to modifi- 
cation, as may partially be inferred from the detailed accounts which have already been 
g'iven. Although a considerable amount of attention has been paid by several observers 
to these variations, and of late years especially by Pansch, Semoff, Huschke, Biidinger, 
Giacomini, Eberstaller, and Cunningham, it cannot be considered as proved that there is any 
constant relationship between any of the variations which are found to occur, and either the 
age, sex, occupation, or even the race of the individual. Various attempts have from time to 
time been made to determine in particular a sexual distinction, but it has invariably appeared 
that the inferences which had been drawn from an insufficient number of observations are not 
borne out by a more extended series. It is more probable that certain racial differences may 
ultimately be established when a sufficient number of brains belonging to individuals of 
other than European races shall been carefully examined, but up to the present the materials 
for such comparison have not been abundant enough. In brains of individuals belonging to 
lower races which have been described (Bushmen, Fuegians, Lapps, and others), it has not 
appeared that there is any distinct lack of complexity in the convolutions as compared with 
ordinary European brains, but it is probable that if a large number were to be examined the 
average complexity in such races would be below that of the average European brain. This 
is in fact stated by Parker to be the case for the brain of the negro, but the number examined 
were not sufficient to be considered conclusive. There is apparently, however, more distinct 
evidence to show that complexity of convolution generally goes hand in hand with intellectual 
development of the individual, for in many cases in which the brains of men of known 
intellectual capacity have been examined, the complexity, due partly to the greater develop- 
ment of secondary and tertiary sulci, partly tc the more curved course taken by the 
principal sulci, has been decidedly, in some instances extraordinarily, marked. Indeed, 
in some cases a relationship seems to have been apparent between a particular type 
of mental development and a special part of the brain ; thus it was found that the brain 
of the great French orator, Gambetta, showed an especial degree of complexity of the third 
left frontal convolution. In skilled artisans it might be expected that the part of the brain 
which is connected with the voluntary movements of the hands and fingers might be found 
to be especially developed, and in one or two individual cases this has been noticed, but the 
material for a general statement regarding such relationship is insufficient. Benedikt^ from 
the examination of the brains of a large number of individuals belonging to the criminal class, 
was of opinion that there exists amongst these an undue tendency to the formation of four 
antero-posterior convolutions in the frontal lobe, or in other words, an undue tendency to the 
appearance of the paramesial and middle frontal sulci. Although apparently supported by a 
few observations by other anatomists, this supposition has not borne the test of more extended 
observation ; and, indeed, the so-called '* criminal " type was actually less frequent in the 
brains of convicts examined by Giacomini than in those of ordinary persons. 




Yarioas explanations have been offered to acconnt for the convoluted form of the cortex. 
These are based partly on mechanical considerations, e.g.y the resiEtance offered bj the larger 
blood-vessels and undue grrowth of the brain as compared with that of its encdosino: skull- 
capsule, partly on physiological or physiologico-mechanical considerations, which suppose 
that there is a relative increase of functional activity of certain parts as compared with others, 
resulting in an increased growth of those parts, and hence their projection in the form of gyri. 
These theories, however, are quite insufficient to account for the convoluted formation, since 
it can be shown (1) that the blood-vessels for the most part do not correspond with the fissures, 
nor do they lie in the depth of the fissures, when they happen to coincide with them ; (2) 
that the brain does not fill the skull at the time the permanent fissures make their appearance ; 
(8) that in the animal series there is no direct relationship between intellectual development 
and cerebral convolution. Further, it may be stated that no theory which will not also 
account for the fissures and laminae of the cerebellum as well as the convolutions of the 
cerebrum can be regarded as satisfactory. 

It has, however, lately been pointed out by Jelgersma that a simple mathematical 
explanation exists for the existence of a convoluted surface. The one feature which mammals 
with smooth brains have in common is smalhiess of body ; whereas those mammals which 
possess convoluted brains are invariably found to be of relatively large size (Dareste). In 
other words, small mammals have smooth brains, however high they may be on the animal 
ladder, and in spite of their possessing a high degree of intelligence (e.g,, certain monkeys), 
whilst large mammals have convoluted brains, although their intellectual development may 
be relatively low (e.g.y cetaceans). " The grey cortex of the brain, which in members of the 
same species maintains a tolerably constant thickness, increases by surface extension. 
Further, with every advance in the growth of the grey matter, there must be a proportionate 
increase of the subjacent white matter. The geometrical law involved is simply this — that 
in the growth of a body the surface increases with the second, but the interior with the third 
power of the radius. From this it is evident, seeing that the proportion of internal white 
matter and external grey matter is in all cases a uniform one, that in the evolution of a large 
animal out of a small animal a disproportion between the grey capsule and the white core of 
the cerebrum must result. This is compensated for by the extended cortex placing itself in 
folds or puckers. Jelgersma further points out that the extent of the cerebral surface 
depends upon two factors, namely, (1) the absolute quantity of the grey matter, and (2) the 
thickness with which this is spread over the surface. The absolute quantity of grey matter 
present is determined by the bulk, or by the psychical endowments of the animal, or by both 
of these factors together. On the other hand, although the thickness of the grey cortex is 
very much the same in the same species, it differs considerably in different animal groups ; 
and it follows from the theoiy which he has advanced that the more sparsely the grey 
substance is spread over the surface of the white matter, the richer will be the convolutian 
type. In the cetacean cerebrum the grey cortex is exceedingly thin, and it is due to this that 
the surface shows such an extreme condition of complexity." ^ 

Cases in which there is a congenital absence of the corpus caUosum are characterized by a 
peculiar type of convoluted surface, the fissures and convolutions showing a strong tendency 
to radiate from the Sylvian fossa. This is partly due, according to Cunningham, to a retention 
of certain of the primitive fissures which appear about the third or fourth month, are due to 
unfoldings of the whole thickness of the cerebral wall, and are mostly quite transitory ; but 
they cannot all be thus accounted for. There is often in these cases an intricacy of pattern 
displayed which is comparable to that of the cetacean hemisphere, and may be very possibly 
produced in a similar manner. 

The same law by which the formation of the cerebral convolutions is accounted for, 
likewise explains the development of the cerebellar folia, and of the wavy outline of the 
corpora dentata of the cerebellum and olives. 

Jelgersma's theoiy is not complete in so far that it does not explain why the convolutions 
should tend to assume certain patterns in certain groups. It is not improbable that these 
differences may be determined by variations in the relative functional importance of 
different parts, producing a corresponding variation in the extent of grey matter which has 
to be provided for, and relative increase of this can only be obtained by local puckering 
(Cunningham). There is no doubt, however, that the formation of the various cerebral 
patterns, fairly constant for the same species, is scarcely susceptible of any very simple 
explanation, and that for the present we must rest satisfied with the statement of the f actb 

^ D. J. Canningham, Address delivered at the opening of the section of Anatomy and Physiology at 
the annual meeting of the British Medical Association, 1890. 




The cerebral hemispheres, like the rest of the encephalon, are composed of white 
and grey sabstance, the white pervading nearly the whole of the middle of each 
hemisphere, where it forms what is known as the medullary centre^ and extending 
into the convolutions ; the grey forming a covering of some thickness over the 
whole surface of the convolutions {cortex), and occurring also at the base of the 
hemisphere in the form of the so-called basal ganglion {corpus striatum). 

The white matter consists of meduUated fibres, varying in size in different parts, 
but in general smaller than those of the cord and bulb. They are arranged in 
flattened bundles separated by neuroglia ; the bundles have a somewhat rod-like 
appearance in transverse section. 

The fibres of the medullary centre, though forming many different groups, may 
be referred to three principal systems, according to the general course which they 
take, viz. : — 1. Frqfection^bres, which pass from the isthmus encephali to the 
hemispheres, or vice versa. These fibres increase in number in passing the optic 
thalami and corpora striata, beyond which they spread in all directions into the 
hemispheres. 2. Trafisverse or commissural /ibreSy which connect the two hemi- 
spheres together, d. Assodation-fihres (Meynert), which, keeping on the same side 
of the middle line, connect near or distant parts of the same hemisphere. 

1. The projection fibres in each hemisphere are continuous in part with the 
fibres of the crusta, in part with those of the tegmentum, the latter probably 
indirectly through the corpus striatum and optic thalamus. They are in great 
measure, if not wholly, direct prolongations of the axis-cylinder processes of cells of 
the cortex (see diagram, fig. 20, p. 23). 

a. The fibres which are continiums with ihose of the crusta pass in the internal 
capsule, between the optic thalamus and nucleus caudatus mesially, and the nucleus 
lenticularis laterally, probably giving off collateral fibres to those ganglia. Beyond 
the internal capsule the fibres diverge into the general white matter of the hemi- 
spheres, forming part of the system of radiating fibres known from its fan-like 
arrangement as the corona radiata (Keil) or fibrous cone (Mayo), the latter term 
being derived from the way in which the assemblage of radiating fibres is curved 
round in the form of an incomplete hollow cone as it emerges from below the 
nucleus caudatus, which follows the curve of the lateral ventricle. 

Although it is probable that most of the fibres of the crusta pass directly into the 
medullaiy centre and through this to the grey cortex, without entering the basal ganglia 
of the hemispheres, this has only been definitely ascertained for one or two of the 
tracts of fibres which run in the crusta. The best known of these is the pyramidal 
tracts which is traceable through the inner capsule (opposite the middle of the lenti- 
cular nucleus) and corona radiata to the grey cortex of the ascending frontal and 
ascending parietal convolutions and to the posterior parts of the first and second 
frontal gyri. This is of interest in connection with the fact that physiological 
experiment indicates the grey matter of these particular convolutions as especially 
concerned in governing the action of the chief groups of muscles of the body (kinass- 
thetic or psycho-motor centres). 

Another group of projection-fibres is the so-called direct sensory tracts which 
passes from the external or lateral part of the crusta through the posterior part of 
the internal capsule into the white matter of the occipital and temporal lobes of the 
hemisphere (centres for special senses). 

The projection-fibres from the prefrontal region pass downwards in the anterior 
part of the internal capsule. 

M 2 


A few of the fibres of the crusta (those nearest the inner or mesial side) do not 
pass into the inner capsale and corona radiata, bnt are collected into the bundle 
known as atiaa leniicularia and pass outwards underneath the thalamus into the 
nucleus lenticularis (see p. 112). 

h. The fibres which pass to the cerebrum in the tegmentum, are originally 
constituted by the longitudinal bundles of the formatio reticularis of the medulla 
oblongata. They are reinforced as they pass upwards by sets of fibres derived from 
the superior peduncle of the cerebellum, and perhaps the middle peduncle ; ^m the 
fillet ; from the deeper parts of the corpora quadrigemina, and from the nerve- and 
other nuclei in the parts which they traverse. They become lost for the most part 
in the subthalamic tegmental region and in the thalamus, but on the other hand, 
from the outer side of the thalamus fibres stream outwards (see p. Ill), and joining 
the general system of the corona radiata, diverge to nearly every part of the hemi- 
sphere. Other fibres, apparently continuous with this same system, pass fi:om the 
posterior part of the thalamus into the optic tract 

From the lower part of the thalamus anteriorly fibres emerge forming the bundle 
known as the inferior peduncle of the thalamus, and curving round below the nucleus 
lenticularis, pass into the white substance of the external capsule. 

2. The transTerae or commiBsural fibres which connect the hemispheres 
together include — a. The transverse fibres of the corpus callosum. b. The fibres of (he 
anterior commissure. 

The fibres of the corpus callosum are derived from the cells of the grey cortex, 
being either the direct prolongations of their axis-cylinder processes or collaterals 
passing off from the projection fibres before mentioned (fig. 20, calL), When, there* 
fore, a portion of cortex is removed or destroyed, certain fibres in the corpus callosum 
undergo degeneration. By this means it may be determined that the anterior portions 
of the callosum contain chiefiy fibres derived from the frontal lobes, the posterior 
chiefiy fibres from the occipital lobes, and the middle poition from the intermediate 
parts of the mantle. The fibres from a limited part of the cortex are not, however, 
entirely limited to one part of the callosum, but show a tendency to scatter, so that 
not only similar but also dissimilar parts of the two hemispheres are connected 
through this commissure (Sherrington). A certain number of projection fibres also 
pass across the callosum to the other hemisphere, and then turn downwards in the 
internal capsule (Hamilton). Hence, after removal of certain parts of the cortex on 
one side of the brain, some degenerated fibres are found in the pyramidal tract which 
is mainly connected with the other side (see p. 31). 

The anterior oommissnre (fig. 118) is composed of a bundle of transverse fibres, 
which chiefly connects the temporal lobes of the two hemispheres. The bundle is most 
compact in the middle line, which it crosses at the front of the third ventricle just 
in iront of the pillars of the fornix : in a median section of the brain it presents an 
oval section of 5 nmi. long diameter, with its long axis from above down. From 
this point it passes laterally as a twisted bundle of fibres curving backwards and 
somewhat downwards through the ventral part of the globus pallidus, and below the 
putamen of the lenticular nucleus. Its fibres then diverge in a fan-like manner 
into the temporal lobe ; whether any pass by means of the external capsule to the 
insula has not been satisfactorily determined. 

The fibres of the anterior commissure which pass into the temporal lobe form by 
far the greater part of the commissure in man, and constitute what has been termed 
by Oanser the pars temporalis. Besides these fibres, there are others which are 
derived from the lobus olfactorius (see p. 160), and which appear to connect the 
olfactory tract of one side with the hippocampal gyrus of the opposite side. These 
form the pars oJfactoria of Ganser : this part is very slightly developed in man. 
The anterior commissure forms the segment of a circle, with the convexity 


directed forwards. It i« the priDCipal cerebral commieanre in all vertebrates below 
mammalg : the corpus callosnm first making its appearance in the lowest mammale 
and becoming developed proportionately with the increase of the mantle. 

Tbe rop«-like twist of the anterior oommiBsure is usooiated b; Hill with a rotation of 
the cerebram, which has occamd in the conree of it« development (Appendix A to EngliBli 
^bauaUtlou of Obersteiner'a "Anatoa; of the Central Nerroua Oivaiu"). 

3. The Msooiatioii-flbrea which connect different parts of the same hemi- 
sphere are either short or long. The thort assodation-flbres (Jibrce propria, Meynert ; 

anawiNa ih» ooprsb 




ventricle, anterior hom ; 
horn ; 8, 6', eoi-pua Btriatui 
7, thaiamOB ; 8, inUmai C 
internal capnale. 

re ; 3, pillara of fornix ; 4, lateral 
5, lateral ventricle, deeoending 
n, caudate and lentioolar nnclei ; 
'apsale ; 8', anterior Begment of 

lamina arcuala gyrorum, Arnold) (fig, 114, s.), 
serve to connect adjacent convolutions, passing 
round below the grey matter at the bottom of the 
fissures. The hng eagociation-ftbret are mostly 
collected into definite bundles, which can be 
traced for a considerable distance between the 
bnndles of cominissural and projection -fibres, or 
which run free for a certain part of their course. 
The principal bundles or tracts of long associa- 
tion-fibres are the following : — ~a 

(fl) Superior association  bundle (superior 
longitudinal fasciculus, fasciculus arcuatus, Burdach). — This consists of st^ttal fibres, 
which tun below the grey matter of the convex surface of the hemisphere, between 
the frontal and occipital lobes, and between the frontal lobe and external part of the 
temporal lobe (Sg. lii,f.l.s.). 

(6) Inferior association- bundle (temporo-occipital bundle, inferior longitudinal 
fasciculus). — This is a bundle of fibres which lies close to the outer wall of the 
posterior and inferior comua of the lateral ventricle and connects the temporal and 
occipital lobes (/.(.!.). 

(c) Anlaior atsociation-bunSe (nncinate fasciculus). — Under this name is 
described a white bundle, seen on the lower aspect of the hemisphere, passing across 
the bottom of tbe Sylvian fissure at the limen insulee, and connecting the frontal 
with the temporal lobe (f.u.). The fibres of this bundle expand at each extremity^ 
and the more superficiaJ of them are curved or hooked sharply between the con- 
tiguous parts of the two lobes, — from which circumstance it has derived tbe name 
nncinate. Its fibres appeal' especially to connect the third frontal gyrus with the 
temporal lobe and with the anterior part of the limbic lobe. 

(d) Cingulum {ci.). — This forms the principal .association-bundle of the gyms 
fomicatuB, its fibres coursing immediately above the transverse fibres of the corpus 
callceam, and passing from the anterior perforated space in front, curve round the 
splenium of the caUosam behind, and pass in the gyrus hippocampi as far as its 
anterior extremity. Some of the fibres diverge, as they pass backwards, into the 
white matter of the hemisphere, and probably reach various parts of the cortex. 
The constitution of this handle and its connections have been already dealt with 
(see p. 168). 

(e) Tbe perpendicular faidculua (Wernicke), which mns vertically immediately 


in front of the occipital lobe and connects the inferior parietal lobnle with the 
fosiform lobule (/-p.). 

{/) Tfis /(WTiw.— This (Jo.), by means of its continuation, the fimbria (JL), 
connects the hippocampa! region of the limbic lobe with the corpna albicans, which 
again is connected through the bundle of Vicq d'Azyr (v.d'A.) with the thalamiu 

Pig. 114. — QiAQKAit or THK 

opticus. The coarse and relations of the fornix have already been described 
(pp. 129, 158). 

The arrangement ot the fibres in the white matter has been studied by H. Sachs, who flndt 
that the fibres in the occipital lobe (the only part as yet fully inyeatigated by him) are arramgad 
jn four layers or series, from within ont, as follows : — 1 . Those which are prolonfred from tiu> 
corpus calloBum (foroeps major), which oocupj the central parts nearest the ventricle. 2. Next 
to these a layer composed of projection-Qbres, passing to the internal capsule. They are flnttr 
than the callosal fibre*. 3. Another layer of larger fibres which snrronnds the projection- layer, 
and is composed of long association-fibres. 4. A layer of short association- fibres, ne*re(rt the 
cortex. It will, of course, be understood that the peripheral layers are constantly pierced by 
the fibres which are passintf from the cortex to join the more oentrally-sttnated layers.; 

STSuaxaRs of usa qnby uatteh. 

The grey matter on the convoluted enrface of the cerebrum forma a continaona 
layer indiBtinctly divided into two or three strata by interposed thin layers of paler 

In examining a section macroscopically from without inwards (fig, 115, 1), we 
meet with — 1. A thin coating of white matter situated on the sorfaee, which on a 
section appears as a faint white line, bounding the grey surface externally. This 
superficial white layer is not equally thick over all parts of the cortical substance 
but becomes thicker as it approaches the borders of the convoluted surface ; it is 


accordingly less conspicuous on the lateral convex aspect of the hemispheres, and 
more so on the convolutions situated in the longitndinal fissnre vhich approach the 
white surface of the corpns cailOBum, and on those of the under anrface of the braiii. 
It is especially well marked on the hippocampal gyms, and it has been there 
described under the name of the retitulated white substance. 2. Immediately beneath 
tbe white layer juab described, is found a layer of grey or reddish grey matter, the 
colour of which, as indeed of the grey substance generally, is deeper or lighter 
according as ita recy nnmerons veesela contain much or little blood. 3. A layer, 
appearing in section as a thin whitish line (line of Vicq d'Azyr, outer line of 

The paria are nearly of ths Dstnral aiie. 1, shows 
the six l»jen ordinaril j aeen in the cereliral eortai when 
carerullj' exHrnined witli the naked eje ; 2, the appear- 
luice of a section of a conTolution from the Detghboar- 
hood of tbe calcariae Amure. 

Baillargor). 4. A second grey stratum. 5. A second thin whitish layer (inner line 
of Baillarger). 6. A yellowish grey layer which lies next to the central white matter 
of the coDvolntion. In some convolutions, especially those bordering on tbe calcarine 
tissnre, the line of Vicq d'Azyr is very distinct, but the inner line of Baillarger is not 
visible (fig. 115, 2). 

Medullated fibres radiate from the white centre of each convolution in all direc- 
tions into the grey cortex, having a course for the most part perpendicular to thu 
free surface. In passing through the grey snbstance they are arranged in bundles 
about TiVath of an inch in diameter, and thus separate the nerve-cells into elongated 
groups, and give the section a columnar appearance (fig. lit!). Tbe direction of 
the fibres varies according to the part of the convolntion in which they occnr, 
whether near the summit or the base, and the radiating direction is somewhat lost 
in the sulci between the convolutions, where the arched fibres which connect the 
adjacent convolutions seem to obscure the radiating bundles. 

Layers of ctiUm in tliB cortex. — The form and arrangement of the cells vary 
at different depths of a convolution, and in this way several layers are distinguished, 
having more or less definite characters, but not sharply marked off from one another. 
Their relation to the stratification distinguishable by the naked eye is not everywhere 
clearly made out. The most common type is that which is seen in the convolutions 
of the parietal lobe. In this most observers agree with Meynert in rec(^ising five 
layers as follows (fig. 116) : — 

1. Superficial or molecular layer. — This, the most external layer, is narrow, and 
forms about y'gth of the whole thickness of the grey cortex. It is composed chiefly of 
neuroglia, but contains some nerve-cells. A few medullated nerve-fibres occur in it, 
forming a thin superficial white stratum almost immediately underneath the pia mat«r. 

As already intimated these fibres are much more developed in the hippocampal 
region than in other parts of the cortex. The layer also contains non-medullated 
fi^es, which ramify in it, and most of which are derived from the peripherally- 
directed processes of the pyramidal cells of the deeper layer. 

The nenrc^lia-cells of the superficial layer are mostly elongated and set perpen- 
dicularly to the surface, where a principal process of each cell nsually terminates in 
a foot or enlargement (fig. 117). 

The nerve-cells of the layer are small. They vary in shape, many being fusiform 
and set parallel with the surface. Both their dendrites and their axis-cylinder 
processes, which give off numerous collateral branches, are for the most part confined 
to this layer. Many of them have two or three axis-cylinder processes, and these 


fteqnentlj come off from the deadritee, instead of, as is naual, from the body of the 
cell (Cajal). 

2. Layer of small pyramids. — This layer, of nearly the same thickneee aa the 

Fig. 116. — SicTioN or cmribrai. oonvoldtioh 
1, HnperGcUl Ujer, with scattered cells ; 2, layer 
of aniall pyr&midal cells ; 3, broader layer of pjra- 
mid&l cells, separated into coluame by the radiating 
uerre-Bbres ; 4, narrow layer of small irregular eella ; 
G, layer of fnsifarm and irregnlar cells in medullar; 

last, is characterized hj containing a large 
nnmber of small nerve-cells, mostly pyra- 
midal, with dendrites extending mainly 
into the soperficial layer, and an axis- 
cylinder process, which starts from the 
base of the cell and afler giving off a few 
collaterals, passes downwards to the white 
centre, possibly to the corpna striatum 
as a projection-fibre. Some of the axis- 
cylinder processes do not, however, reach 
the white matter, but end in arborisations 
between the cells of the next layer. 

3. Layer of large pyramids. — The third 
layer is of paler tint and much greater 
thickness. It contains pyramidal branching 
cells, some large others smaller, arranged 
with the pointed extremities towards the 
surface of the convolution, and separated 
into groups by the bandies of radiating 
nerve-fibres. The innermost portion of the 
layer, in which the cells are larger and the 
separation into groups more distinct, is 
sometimes described as a separate layer. 
The axis-cylinder processes of these cells 
give off 7 or 8 collaterals, which become 
medallated and end by ramifying in the 
adjacent grey substance. The axis-oylin* 
der is then continued on into the white 
matter as a medullated fibre. 

4. Layer of polymorphous cells. — The 
fourth layer is narrower, and contains 
many small, irregularly-shaped corpuscles, 
with numerous dendrites and a single aiis- 
cylinder process. The axis-cylinder pro- 
cesses of most of these cells tend towards 
the white centre, but some pass periphery 
ally, and reach the molecular layer where 
they become continuous with some of the 
nerve-fibres of that layer. 

5. Layer of fusiform cells. — The fifth 
layer, of greater width than the last, and 
blending more or less with it, is com- 



posed of fasif orm and irregalar cells. The f asif onn corpuscles have a definite arrange- 
ment, being placed for the most part vertically at the sommit of a gyros ; but parallel to 
the surface in the solci, where they correspond in direction to the arcuate fibres passing 
from one convolution to another ; they are said to be connected with these fibres. 

Fig. 117. — Cklls from thb cbrxbral 


(Q, Retidas.) 

n,n, nenroglia-oells ; p,p, pyramids ; 
a,a, axiB-cylinder processes of pyramids 
giving off collaterals. 

Beneath the last layer is the 
medullary centre, with which it gra- 
dually blends. The fibres of the 
white substance^ as they radiate into 
the grey matter, become finer. They 
are mostly continuous with the axis- 
cylinder processes of the pyramidal 
cells, the collaterals of those forming 
two plexuses of medullated fibres 
which lie, the one at the base of the 
8rd layer, the other between this 
and the 2nd layer. These plexuses 
(inner and outer white plexuses of 
W. Krause) are probably the cause 
of the lines of Baillarger seen with 
the naked eye in a section of the 
grey cortex of a fresh brain. 

In the Sylvian fissure the fusi-. 
form cells are more abundant than 
elsewhere, and from their numter 
in the claustrum the fifth layer has 
been termed by Meynert the '' claus- 
tral formation.'' They are also very 
abundant in the amygdaloid nucleus, 
which is indeed chiefly formed by a 
thickening of the deepest layer of 
the cerebral cortex. The comu 
ammonis on the other hand is formed 
almost exclusively of the large pyra- 
midal cells, and the layer in which 
these occur (third layer) has, in 
like manner, been termed the " for- 
mation of the comu ammonis." 

The axis-cylinder processes of the 
pyramids when they reach the medul- 
lary centre, pass either as association-fibres to other parts of the cortex of the same 
hemisphere, or as commissural fibres to the corpus callosum, and through this to the 
opposite hemisphere, or as projection-fibres to the corpus striatum and optic 
thalamus, or by way of the internal capsule to the midbrain, bulb and spinal cord. 
The junction with fibres of the association-bundles may be T-shaped, in other words 
they may bifurcate and pass in opposite directions underneath the cortex. Eventually 
they turn into the cortex again and end by free arborisation amongst its cells. More- 


''■:U ^-if 



■'( • w. 


Fig. IIS. — Sioiioa or oobtuc o 

Fig. 119.— Skctioh or oobtu 
The DDmbcra dcDote Ibe laiiifl layers an ia fig. 118. 

Fig. ISO.— SiimoR or cortix or raontAL lobi. 
1, 2, u in fig. 118 ; 3, 4, large pfnuuidi ; 5, polymorphoos wid apiudlB-cellj. 




■if) ■'■',' J^: 


The Dnniberx deaate th« biid« )&;«is u id Gg. 1'20. 


1, anperSdal lijer ; 2, thort pfmnida ; 3, long p;niiuda. 


over, in their longitudinal course they give off collaterals here and there to inter- 
mediate parts of the cortex. The commissural fibres, after passing through the 
corpus callosum, have a longer or shorter course in the white matter of the^ opposite 
liemisphere, and end by terminal arborisations in its cortex. In their course they also 
give collaterals to other parts of the cortex. Some of the commissural fibres are 
themselves collateral branches of the projection-fibres (fig. 20, p. 23). 

The projection-fibres pass for the most part into the internal capsule. Both 
before reaching this and as they pass through it they give off collaterals, some of 
which enter the basal ganglia and ramify amongst the cells, whilst others pass 
towards the corpus callosum. The main fibres ultimately end' by arborisation in 
the grey matter of the lower nerve-centres : those of the pyramidal tract amongst 
the cells from which the motor nerve-fibres originate. The projection fibres are 
mainly derived from the middle-sized and larger pyramids, and from some of the 
polymorphous cells of the fourth layer.^ 

Differences of stmctnre in different parts. — Considerable variety occurs in 
different parts of the cerebral cortex in the size and regularity of shape of the nerve- 
cells and in the relative thickness of the several layers. It is especially worthy of 
notice that in the '' psycho-motor *' region, and particularly in the upper part of the 
ascending frontal convolution, some of the deeper pyramidal cells are very large 
(fig. 121, 4), and are arranged in more or less defined groups or nests (Betz, Bevan 
Lewis). On the other hand, in the neighbourhood of the calcarine fissure, large 
cells are very scanty, their places being for the most part taken by smaller ones 
(fig. 118). Again, in many parts a six-laminated cortex is produced by the interca- 
lation of a layer of small angular cells in the middle of the layer of large pyramids 
(figs. 118, 119). 

These differences in the size and arrangement of the cells in different parts of 
the cortex are well illustrated in the accompanying figures (118 to 123) by Bevan 
Lewis of sections from various regions. 

The most remarkable differences of structure occur at the margin of the hemi- 
sphere in the region of the hippocampus, and in the olfactory lobe. These will now 
be specially considered. 

Stmctnre of the hippocainpns ni%jor or comn ammonis. — The hippo- 
campus it will be remembered corresponds to the hippocampal fissure externally ; 
this fissure separating the uncinate or hippocampal convolution below from the 
fascia dentata above. The uncinate convolution (fig. 123) has the ordinary structure 
of the cerebral gyri, being composed of a grey cortex and a thick white centre. 
The cortex generally is, however, thin, but the superficial layer is relatively thick, 
and contains many medullated fibres. The cells of the second layer are relatively 
large as compared with other parts of the cortex. The cortex is prolonged around 
the hippocampal fissure, forming the main part of the hippocampus (figs. 110, 124) ; 
the white centre is also prolonged over the projection of the hippocampus into the 
Ventricle, but becomes very thin in this situation where it is known as the alveus. 
It is covered by the epithelium and ependyma of the ventricle. 

Above the hippocampal fissure the grey matter of the hippocampus swells out 
into the notched lamina known as the fascia dentata (dentate convolution, fig. 124, 
F d). The white matter of the alveus is in like manner prolonged over this, but not 
quite as far as its free border ; it becomes thickened and is continuous with the 
white band known as the fimbria {Fi), which thus represents a free edge of the 
medullary centre of the hemisphere. 

The projection of the hippocampus (into the ventricle) is thus produced by the 

^ Most of the aboTO details relating to the destination of the axis-cylinder proeesses are derired from 
the observations of Bamdn y Cajal, made upon specimens prepared by GK>lgi*B method. 


inraginatioD of the cortex as the hippooampal fisBiire. Accordiag to Oolgi and Sala 
there i8 a second ioTagination into the fascia dentata : this must however be looked 
upoa as quite incomplete. 

The greater part of the grey matter of the hippocampus is ocx:apied by aeveral 
rows of moderately large pyramidal cells (fig. 122, 5 ; fig. 124, S) with long apical 
processes, which lie embedded in a nenroglia-matrix, and confer npoa this, especially 


(after Heole). 
Oh, put of the gymi hippocampi or uncinate conTolution ; Fd, fiucia dentata or dentCita CDavola- 
tion ; between them ia the dentate fiBsura ; Fi, fimbria, composed of longitudinal Sbres here cut across ; 
1, 2, medullar; centre of the hippooampal gjrus prolonged around the hippocampus, H, aa the so-called 
alreua, into the fimbria ; S, Uyerof large pTmmidal cells ; 1, stratum radiatum ; 5, stratum laciuiosum ; 
0, superficial inedallai7 lamina, inToluteil around the dentate fisanre ; **, termination of this lamina, 
the fibres here running longitudinally ; 7, anperficial neuroglia of the fascia dsntala ; *, stratum 

in its outer part, a striated aspect ; hence the name of stratum radiatum sometimes 
nsed to distinguiah this part of the layer (i). By their bases the cells rest upon the 
white layer or alveus, into which their azta-cyliDder processes pass, but there is in 
some parts a layer of grey matter intervening (fig. 122, G). 

Superficial to the stratum radiatum, the processes of the pyramidal cells form an 
arborisation, the branches of which are closely interwoven {stratum laciniosum, 5). 
Superficial to this are a lai^ number of small cells which give a grannlar appear- 


ance to the lajer thej occapy (stratum ffranulosum). Superficial to this again is a 
well-marked layer of medullated fibres continnoaa with the reticalated white subBtance 
of the uncinate convolution (see p. 156). It is known as the involuted medultari/ 
lamtTia (fig. 124, 6), and represents an increased developmeot of the thin layer of 
white fibres wiiich is ordinarily found in the molecalar or superficiftl layer of the 
grey matter. 

In the fascia dentata the large pyramidal cells are placed in the ceatre and arc 
irregularly arranged : they are surrounded by an incomplete ring of closely packed 
small pyramidal cells {stratum granulosum, fig. 124, "), outride which is a very 
broad superficial layer of neuroglia with a few scattered cells, 

Xinnta Btractara of the olftkctory lobe. — The pecuUar stroctare of this part 
of the brain can best be understood by a reference to its mode of development. It 
is formed as a hollow outgrowth from the vesicle of the cerebral hemisphere (after- 

r, vsntral snrfiiro ; d, danttl ridge. From without in an Keen 
mocflsaivelr : (Ija thin superioiil layer of aeumglia j (2) n Idmrkly 
Khiuled) layer of tnmsTersolj-cut medulhuy fibcea, of veiy aneqiul 
thicknesa in different parts ; (3) the central grey matter prajeeting Dp 
into the dotBal ridge and here and there extending to the SDrface and 
jATtiaUj interrupting the meduUoi; layer. 

wards the lateral ventricle), and in most of the lower 
animals (in which it is much more developed than in 
man), it exhibits even in the adult condition a central 
-J- cavity (lined with ciliated epithelium), and in some, as 

already stated, this retains thronghout life its connec- 
tion with the lateral ventricle. The walls of the hoUow outgrowth become 
thickened and differentiated into a central layer of neuroglia next to the cavity, 
a well-marked intermediate layer of white substance outside this, and a peripheral 
layer of grey matter surrounding the whole. In man and apes the same changes 
occur, bat the cavity becomes completely obliterated and in its stead we find nothing 
but central neuroglia, which forms for the most part a tract flattened out laterally, 
and containing but few cells. The white or medullary substance around this appears 
in section in the form of a flattened ring consisting of longitudinal white fibres 
(fig. 125). In the olfactory tract the peripheral layer of grey matter is very thin 
and inconspicuous, so that the white substance almost everywhere shows through it, 
except along the dorsal ridge where there is an accumulation of the grey Bnbstance, 
extendii^ into and partly interrupting the medullary ring (fig. 125, rf)- la l-he 
bulb on the other hand this dorsal accumulation of grey matter is not seen ; but 
upon the ventral side of the fiattened medullary ring (fig. 126, 1, 2, 3) in place of 
the thin scarcely visible layer of grey substance in the corresponding situation in 
the tract, a thick layer of grey matter is found and forms indeed the greater part of 
the thickness of the bulb, what was originally the central cavity being consequently 
now placed near the dorsal surface. This grey matter aa seen in section exhibits 
the following parts (fig. 126, 4 to 8) :— 

(1.) A granvle Uyer of considerable thickness (fig. 126, 4, 5, 6) lying next to the 
medullar? ring, and characterised by the presence of numerons smaU cells, like those 
found in the deeper or granule layer of the grey cortex of the cerebellum. The 
layer is not entirely composed of these cells however, for there are present in addition 
a number of reticulating bundles of mednliated fibres which separate the " granules " 
into groups, and other meduUated fibres which pass vertically between the medullar; 
ring and the next layer. There are also a number of lai^e nerve-cells, having for 
the most part a conical shape {mitral cells, fig. 137, m.c,), the axis-cylinder processes 


of which pass npwards through the grannie bjer, while most of their protophtamic 
or dendritic processes enter the next stratam. 

(2.) yAe layer of olfactory glomeruli (7). The reniarkable bodies which 

Vig.l2S.— SHmomi 

1, 3, Ujen of Tarj fioe truu- 
T«nelf eat aerv«-fibres, puaing 
roond into one uiothei at the 
Bids, and fonuiDg the Sattennl 
medulluy ring, encloaiDg the can- 
tnJ neoTDglia, 2 ; 4,5, 9, granule- 
lajBr 1 7, lajer of olfactory glome- 
rnli, ti ft ; 8, lojer ot olfaotorj 
nerre-fibns, bundles of which are 
■esn passing at * * to the alfactorj' 
naooui membraii«. 

charaoterize this stratDin 
were first described by Ley- 
dig in elasmobranchs and 
by Lockhart Clarke in 
mammals. Theyareronnded 
bodies which are formed of 
a dense interlacement of 
nerve-fibres derived on the 
one hand from the dendrites 
of the mitral cells, on the . 

other from the olfactory * 

fibres of the next layer. Theya]8oincludeafew8maUcells,nhich are probably neuroglial 
(3.) The layer of olfactory nerve-Jibres (8). This, the deepest layer of the bulb, 

Fi|. 127.— DiaoiAM or the 

BELB. (E. A. 8.) 

otf.e., cells of the olfactory 
mncoofl meinbnne ; ol/.n^j 
deepest layet of the bulb com- 
posed of the olfactory nerre- 
fibna, which are prolonged 
from the oUactor; cells; gl., 
olfactory glomerali, containing 
arborisations of tbe olfaclocy 
nerve-fibres and of the den- 
drites of the mitral cells ; m-c, 
mitral cells ; a, their aiie- 
cylinder procesaes pawing to- 
wards tbe nerre-Gbre layer,, of the bnlb to become 
eontinaODi with fibres of the 
olfactoiy tisct : these aiis- 
cylindsr processes are seen to 
give off collaterals, some ot 
-which pans again into the 
deeper layers of tbe bnlb ; 
n', a nerre-Gbre from the 
alfactory tract ramifying in 
the grey matter of the bulb. 

oonsiBts entirely of bundles of non-medullated nerve-fibres, which here form a dense 
plexus the fibres of which on the one band pass through the perforations in the 


cribriform plate of the ethmoid bone to the olfactory mucous membrane, and on the 
other hand into the glomeruli, where they ramify and form^ arborisations, which 
interlace with those of the dendrites of the mitral cells. 

The relations of cells and fibres in the olfactory bulb have recently been reinvesti- 
gated by Golgi, Ram6n y Cajal, v. Gehuchten, and others, by the aid of Golgi's silver 
nitrate method. The result of these investigations has been to show that the 
olfactory nerve-fibres take their origin in the olfactory cells of the Schneiderian 
membrane, which are therefore to be regarded as peripheral nerve-cells, and that 
they terminate in the arborisations already mentioned as occurring in the olfactory 
glomeruli. To these same glomeruli protoplasmic processes of the mitral cells also 
pass and end in arborisations which intimately interlace with those of the ol&ctorj 
fibres. (Some of the protoplasmic processes of these cells do not, however, pass to 
the glomeruli, but end in free arborisations in the deeper parts of the granule layer.) 
On the other hand the axis-cylinder processes of the mitral cells pass upwards from 
the rounded apex of the cell, and passing between the *Vgranules ** reach the white 
fibres of the medullary ring. Turning sharply backwards nearly at a right angle 
they then become continuous with the fibres of the ring (see fig. 127), ultimately 
reaching the olfactory tract, along which they are conducted to the base of the 
brain. As they pass upwards and also in their horizontal course, they give off 
collateral fibres to adjacent parts of the bulb : these collaterals end after a shorter 
or longer course in free arborisations in the grey matter. 


Bimenflions. — The length of the cerebral hemispheres, measured from the 
frontal to the occipital pole, varies in the larger proportion of cases between 160 mm. 
and 170 mm. for the male brain ; and between 150 mm. and 160 mm. for the female 
brain. The greatest transverse diameter of the whole brain for both sexes is about 
140 mm. and the greatest vertical measurement of each hemisphere about 125 mm. 
(Huschke). The brains of dolichocephalic individuals are naturally longer than 
those of brachycephalic : in the latter there is a tendency to a breaking up of the 
longitudinal gyri by transverse fissures, thereby increasing the amount of surface 
and hence of grey cortex in proportion to the whole brain. 

Extent of grey cortex. — The attempts hitherto made to measure or estimate the 
relative proportions of the different convoluted parts of the cerebrum to each other 
and to the degree of intelligeuce, either more directly or by the cranioscopic methods, 
have been attended with little success. Sach researches as those of Rudolph Wagner 
give, however, some promise, when fully earned out, of affording more definite 
results. These researches had for their object to institute an accurate comparison 
between the brains of certain persons of known intelligence, cultivation, and 
mental power, and those of persons of an ordinary or lower grade. As examples of 
brains of men of superior intellect he selected those of Professor Gauss, a well-known 
mathematician of eminence (set. 78), and Professor Fuchs, a clinical teacher 
(sBt. 52) ; and as examples of brains of ordinary persons, those of a woman of 29 
and a workman. 

The carefdl measurement of all the convolutions and the intervening grooves in 
the four brains above mentioned was carried out by H. Wagner, by covering the 
cortex everywhere with gold-leaf, and determining the extent of surface by the 
amount employed. The result of these measurements is partly given in the 
accompanying table, the numbei's indicating square millimeters of surface. 

It will be seen that although there are undoubtedly differences in the brains 
examined, these are by no means so striking as might have been expected. Indeed 
it may be stated that the general result of these and similar observations has been 



hitherto inconclusive, for although there have hoen observed several notable instances 
in which superiority of intellect has been found to be accompanied bj increased size 
or complexity of the cerebral surface, in many other cases no such relation has been 

Comparaiive measurement of the extent of surface of the cerebral convolutions. 

j]e OF XACH Lobe separatkly. 

Free and Deep sur- 
faces OF Convolutions. 

surface of 






Tsv^ ' Deep surface, 
suiS^e Including sur- 
surace. fece of insula. 

1. Gauss 

2. Fuchs 

3. Woman ... 

4. Workman., 










It will be seen irom the above that the total surface, exposed and sunken, is 
about 200,000 squate mm., and that there is about twice as much sunken as 
exposed surface. With this estimate the determinations made by subsequent 
observers mostly agree. Baillarger, who dissected off and unfolded the cortex, aud 
then measured its whole extent, obtained only an area of 170,000 sq. mm. as 
the mean of the brains thus treated. Paulier, by a modification of the method of 
Wagner, obtained a result similar to that of Baillarger for the whole surface, and, 
further, found the sunken surface to measure but little more than the exposed 
surfEu^e, and the extent of surface to bear no relation to the weight of the brain. 
Oalori measured 41 brains (Italians), and obtained the following average results (in sq. 
mm.) for the total surface : — Male, brachycephaliCy 248,778. Male, dolichocephalic, 
230,212. Female, brachycephalic, 211,701. Female, dolichocephalic, 198,210. 

Danilewsky attempted to determine the area of the whole cortex by a comparison 
of the weight of the brain, its specific gravity (1088), the specific gravity of the 
grey matter (1088), and white matter (1041), and the average thickness of the grey 
matter, which he estimated at 2*5 mm. He obtained in this way a result of about 
S3 per cent, as the weight of the grey cortex, giving for a brain weighing 1824 grm., 
a total surface of 169,200 sq. mm. De Begibus made similar calculations from 
estimation not of the specific gravity but of the amount of water in the whole brain 
and in its two component substances. His estimates of the total area of the corte.< 
of both hemispheres are higher than those of Danilew^sky, varying from about 
217,472 to 278,940 sq. mm. (vide Donaldson "On the Brain of Laura Bridgman,** 
in the American Journal of Psychology, vols. iii.Jand iv.) 

Thickness of cortex. — It is clear that a measurement of surface alone without 
taking into account the thickness of the cortex, may be entirely misleading as to the 
amount of grey matter in the brain. This has been recognized by various observers, 
who have accordingly endeavoured to form an estimate both of the average thickness 
of the cortex generally, and also its thickness in special localities. The results have 
been tabulated by Donaldson in the paper above referred to, and from them it 
would appear that the thickness may vary from 1*55 mm. to 8*6 mm., or even 
somewhat more than this, the average in normal brains being 2*9 mm. If 
a section be made across a gyrus it will be found that the cortex is thickest at the 
summit of the gyrus and thinnest at the bottom ofi the bounding sulci, so that it is 
necessary to take a mean between these two measurements in order to arrive at the 




average thickness for anj locality. But beyond the fact that the cortex is somewhat 
thinner near the hemisphere-poles, and especially the occipital pole, than in the 
intermediate parts, no definite statement regarding the relative thickness of difiPerent 
parts can at present be made. Females have a very slightly less thickness of cortex 
than males (less than 1 per cent.), and the right hemisphere less than the left : the 
diflference may amount to 7 per cent. (Donaldson). 

Weight. — The results obtained by Sims, Clendinning, Tiedemann and J. Reid 
showed the maximum weight of the adult male brain, in a series of 278 cases, 
to be about 1810 grammes (64 oz.), and the minimum weight about 960 grammes 
(84 oz.). In a series of 191 cases, the maximum weight of the adult female brain was 
1585 grammes (56 oz.), and the minimum 880 grammes (31 oz.). In a very lai^e 
proportion the weight of the male brain ranges between 46 oz. and 53 oz., and 
that of the female brain between 40 oz. and 47 oz. Similar statistics have been 
publiMied by Peacock, R. Wagner, BischofiT, Huschke, Boyd, Weisbach and others. 
The mean weight at from 20 to 40 years of age was found by Boyd to be 48 oz. 
(1360 grammes) for the male, and 43^ oz. (1230 grammes) for the female brain. 
Although many female brains exceed in weight particular male brains, as a general 
fact it may therefore be affirmed that the adult male encephalon is on an average 
heavier by 4 oz. or 5 oz. than that of the female (or about 9 per cent.). 

The appended table, which has been compiled from the observations of R. Boyd 
^Phil. Trans. 1860), shows in grammes the mean weights at different ages in the 
two sexes. 

Males. Femaleh. 31ales. Females. 

Children stiUborn at term... 393 ... 347 From 14 to 20 yeai-s 1,374 ... 1,244 

Children born alive at term . 330 ... 283 From 20 to 30 years 1,333 ... 1.237 

Under 3 months 493 ... 451 From 30 to 40 years 1,364 ... 1.220 

From 8 to 6 months 602 .. . 560 

From 6 to 12 months 776... 727 

From 1 to 2 years 941 ... 843 

From 2 to 4 years 1,096... 990 

From 4 to 7 years 1,138 ...1,135 

From 7 to 14 years 1,301 ...1,154 

From 40 to 50 years 1,351 ... 1,212 

From 50 to 60 years IM'd ... 1,220 

From 60 to 70 years 1^313 ... 1,208 

From 70 to 80 years 1,288 ... 1,168 

Over 80 years 1.283 ... 1,125 

It would appear from the above that the brain is absolutely heavier between 14 
and 20 years of age than at any other period of life, and that at the age of 80 it has 
lost about 90 grammes, or rather more than 3 ozs., i.e., about yV o^ its whole w^eight. 

The figures obtained by Broca are somewhat higher than these, e.g., between the 
ages of 80 and 36, in the male, an average of 1421 grammes (50 oz.) ; in the 
female, 1269 grammes (45 oz.). According to the same statistics, the weight of the 
brain attains its maximum, not before the age of 20, as found by Boyd, but between 
25 and 35 in the male and a little earlier in the female. This agrees with the 
results of Peacock. 

The two hemispheres of the same brain, although hardly ever of exactly the 
same weight, show no constant difference, the one half preponderating just about as 
often as the other, and the average difference being only about 5 grammes (Branne). 
There is no evidence that the right hemisphere is the heavier in left-handed people. 

It has frequently been found that the brains of distinguished men have a brain-weight 
aboye the average, sometimes markedly so, but the rule has many exceptions. The oonverse 
is by no means true. 

The relative weight of the encephalon to the body is liable to great variation ; 
nevertheless, the facts to be gathered from the observations of Clendinning, 
Tiedemann, and Reid, furnish the following general result. In a series of 81 males, 
the average proportion between the weight of brain and that of the body at the ages 
of twenty years and upwards, was found to be as 1 to 86*5 ; and in a series of 82 
females, to be as 1 to 36*46. The results of Bischoff's observations give 1 to 35*2 in 



the female. In these cases the deaths were the result of more or less prolonged 
disease ; but in six healthy individuals dying suddenly from disease or accident, 
the average proportion was 1 to 41. 

The proportionate weight of the brain to that of the body is much greater at 
birth than at any other period of extra-uterine life, being, according to Tiedemann, 
about 1 to 5*85 in the male, and about 1 to 6*5 in the female. From various 
observations, it further appears that the proportion diminishes gradually up 
to the tenth year, being then about 1 to 14. From the tenth to the twentieth year 
the relative increase of the body is most striking, the ratio of the two being at the 
end of that period about 1 to 80. After the twentieth year the general average of 
1 to 86 '5 prevails, with a further trifling decrease in advanced life. 

Influence of stature on brain weight. — According to J. Marshall, the proportion 
of entire brain (in ozs.) to each inch of stature, is for the male sex 0'708 ; in 
the female 0'688. This relative preponderance in the male is due entirely to pre- 
ponderance of cerebral development ; the average stature-ratio for cerebrum alone 
being 0*0619 oz. in the male per inch of stature, and 0*599 oz. in the female, 
whils the stature-ratios of cerebellum, pons and medulla oblongata, are similar in 
the two sexes. 

The following tables have been compiled by Marshall from the data furnished by 
the observations of R. Boyd upon the brains of 1150 sane persons, viz. : — 598 males 
and 552 females. They show the average weights in ozs. of the encephalon and its 
several parts at certain periods of life and in individuals having certain differences 
of stature : — 





Stature 68— ( 


Stature 66 inches and 















1 a p 


, 5 





Bd. Ob 





5d. Ob] 






9d. Ob] 





S9^ ' 
















1 1 







41 15 







6 09 

-96 i 

47-08 41-01 












-93 ' 

46- 40-1 



\ 44-15 



















Total nninber of 



Stature 64 inches and 


Stature 63—61 inches. 

Stature 60 inches and 











Pons and 
Med. Obi. 






Pons and 
Med. Obi. 








Pons and 
Med. Obi. 













4-85 -9 
4-56 -9 ! 
4-66 -84 



i 89-69 









•82 ' 





-89 ' 41-58 1 86-17 4-6 -86 

N -Z 


It will be seen from these that although there is an increase of brain-weight with 
body-stature, this increase does not keep pace, pari passUy with the stature. That 
is to say, taller persons, although they have absolutely more brain substance, have 
relatively less than shorter persons. This is true for either sex. Nevertheless the 
proportion of brain to the stature remains larger in the male both at the mean height 
of both sexes, and at nearly corresponding heights. 

Marshall further finds from a minute analysis of these results of R. Boyd, that in the case 
of males of mean height, the weight in ounces of the cerebrum may be obtained by simply 
dividing the number of inches of height by 1*6, or in g^rammes by multiplying the number of 
centimetres of height by 7. 

For females, the same formula as that employed for the male can be used, but the result 
must be multiplied by J^. 


Height in inches 
Weight in ozs. of the mean male cerebrum = - 

female cerebrum=- - " ,., — x fl 

Height in inches 


Weight in grammes of the mean male cerebrum = Height in oentim. x 7 

female cerebrum = Height in oentim. x 7 x |{ 

j» »j 

The weights as calculated from these formuls are found by Marshall to correspond vety 
nearly with the observed weights for definite statures as recorded in Boyd*s tables. The 
correspondence is most complete for statures near the mean, the observed weights being 
slightly defective at the higher, and excessive at the lower statures.^ 

Most of the estimates of brain weight in different races have been obtained as 
the result of measuring the cubic contents of the skull cavity (compare Vol. II., 
p. 83, and Manouvrier, be. dt.). In this way it is estimated (Davis), that the 
Chinese have an average brain weight of about 1330 grammes (approaching that 
of the European) ; the Sandwich islanders one of 1300 grammes ; the Malays and 
North American Indians one of 1265 grammes; the negro 1245 grammes; the 
native Australians 1185 grammes. The Hindus have also a small brain weight 
(probably in relation to the small prevailing stature), viz. : 1 190 grammes. Amongst 
Europeans the Latin races have a somewhat less brain weight than the Teutonic and 
Sclavonic races ; here also in all probability the influence of stature is apparent. 

Weight of the several parts of the enoephalon. — The proportionate 
weight of the cerebellum (inclusive of the pons and the medulla oblongata) to that 
of the cerebrum is, in the adult, as 18 to 87 (Huschke). The cerebellum is both 
absolutely and relatively somewhat heavier in the male than in the female. 

In the new-bom infant the ratio of the weight of the cerebellum to that of the 
whole brain is strikingly different from that observed in the adult. Huschke found 
the weight of the cerebellum, medulla oblongata, and pons together in the new-bom 
infant, as compared with that of the cerebrum, to be in the proportion of 7 to 98. 

Meynert found the proportions between the frontal, parietal, and conjoined 
occipital and temporal lobes to be 41*5 : 23*4 : and 85*1 (in both the male and 

Weight of the spinal cord. — Divested of its membranes and nerves, the 
spinal cord in the human subject weighs from 1 oz. to 1| oz. (average 30 grammes, 
Schwalbe). Its proportion to the encephalon is about 1 to 48. 

^ For further diMussion of the proportion of statare to hrain weight, the reader iB referred to a 
paper by le Bon in the Revue d*Anthropol. , 1879, and to one by the late Prof. J. Marshall, F.R.S., in 
the Journal of Anatomy and Physiology, July, 1892. 



The cerebro-spinal axis is covered b; three membranes, named also meninges. 
They are : — 1. An external fibrous membrane, named the dura maler, which lines 
the interior of the sknil, and forms aloose sheath in the spinal canal ; 2. An internal 
areolar and vascular tunic, the^ maler, which closely covers the brain and spinal 
cord; and 8. An intermediate non-vascular membrane, the arachnoid, which lies 
over the pis mat«r, the two being in some places in close connection, in others 
separated by a considerable space. 


The dura mater is a very strong dense inelastic fibrous tunic of considerable 
thickness ('5 mm. or more in the cranium, less in the spinal canal). Ita inner 
surface, turned towards the brain and spinal cord, is smooth and lined with 


and Betiius.) 
B, bandies o( the nerre-root becoming 
collected into  aingle buniile u they 
emerge ; 6, dura miitcr ; c, arachnoid ; 
d, > reticulnr luoella of the arachnoid 
nflected along the narTt-rnot ; i, sub- 
dural space ; >', ■', subsrachnoitl space. 

epithelinm (endothelium), which » 
was formerly regarded as a parie- 
tal refiection of the arachnoid 
membrane, this having been '' 
generally looked upon as a 
serous membrane. The space 
between the dura mater and 
arachnoid was formerly in like 
manner regarded as the sac of 
the arachnoid, but is now con- 
veniently termed the gubdural 
tyice. The outer surface of the 

dura mater is connected wich the surrounding parts in a somewhat different manner 
in the cranium and in the spinal canal. 

In the cranium it adbei'es to the inner surface of the bones, and forms their 
internal periostenm. The connection between the two depends, in a great measai'e, 
on blood-vessels and small fibrous processes, which pass from one to the other ; and 
the dura mater, when detached and allowed to float in water, presents a flocculent 
appearance on its outer surface, in consequence of the torn parts projecting from it. 
The adhesion between tlie membrane and the bone is more intimate apposite the 
sutures, and also at the base of the skull, which is uneven, and perforated by 
numerous foramina, through which the dura mater is prolonged to the outer surface, 
being there continuous with the pericranium. The fibrous tissue of the dura mater 
becomes blended with the areolar sheath of the nerves at the foramina which give 
exit to them. 

In leaving the skull, the dura mater is intimately attached to the margin of 


the foramen magnam, and below this to the cervical vertebrae as far as the third. 
Above the atlas it has an orifice on each side for the passage of the vertebial artery. 
Within the rest of the vertebral canal it forms a loose sheath around the cord {thsca)^ 
and is not adherent to the bones, which have an independent periosteum. Towards 
the lower end of the canal, a few fibrous slips proceed from the outer surface of the 
dura mater to be fixed to the vertebrae ; one such being especially well marked at the 
lower end, and seeming to join the anterior surface of the dura mater to the posterior 
common ligament of the vertebrae (anterior ligament of the dura mater, Trolard). 
The theca ends opposite the second sacral vertebra in the adult (see p. 6). The 
space intervening between the wall of the canal and the dura mater {epidural ^pace) 
is occupied by loose fat, by areolar tissue, and by a plexus of spinal veins. 

Opposite each intervertebral foramen the dura-matral theca has two openings, 
placed side by side, which give passage to the two roots of the cwresponding spinal 
nerve. It is continued as a tubular prolongation on each nerve (fig. 128), and is 
lost in its sheath. Besides this, it, is connected with the circumference of the 
foramen by areolar tissue. 

The fibrous tissue of the dura mater, especially within the skull, is divisible into 
two distinct layers, and at various places the layers separate from each other and 
leave intervening channels, called sinuses. These sinuses, which have been else- 
where described (Vol. II.), are channels for venous blood, and are lined with a 
continuation of the endothelium of the veins. The division into two layers is most 
complete at the base of the skull, in the middle fossa, and in the neighbourhood of 
the cavernous sinus ; on the outer side of this the Gasserian ganglion is included in 
a space (cavum Meckelii) between the two layers. Between the two cavernous 
sinuses the pituitary body is received into a depression of the membrane, which 
closely surrounds the organ in question, except where the infundibulum enters it. 
There is further a fissure immediately over the orifice of the aquaeductus vestibuli, 
and here the prolongation of the membranous labyrinth of the ear, known as the 
saccus endolymphaticus, is received between the two layers. 

The dura mater also sends inwards into the cavity of the skull three strong 
membvdJiQxia processes or partitions. Of these, one descends vertically in the median 
plane, and is received into the longitudinal fissure between the two hemispheres of 
the cerebrum. This is the falx cerebri. The second is a sloping vaulted partition, 
stretched across the back part of the skull, between the cerebrum and the cerebellum, 
named the tentorium cei-ehelli. Below this, another vertical partition, named fdlx 
eerebelliy of small extent, passes down between the hemispheres of the cerebellum. 
Lastly, the portion of dura mater which stretches over the sella turcica, and pierced 
by a small hole for the infundibulum, covers the pituitary body, is sometimes spoken 
of as the operculum or tentorium of the hypophysis. 

The fiJx cerebri (fig. 129, 1) is narrow in front, where it is fixed to the crista 
galli, and broader behind, where it is attached to the middle of the upper surface of 
the tentorium, along which line of attachment the straight sinus is attached. 
Along its upper convex border, which is attached to the middle line of the inner 
surface of the cranium, runs the superior longitudinal sinus. Its under edge is 
free, and reaches to within a short distance of the corpus callosum, approaching 
nearer to it behind. This border contains the inferior longitudinal sinus. 

The tentorium cerebelli, or tent (fig. 129, 8), is elevated in the middle, and 
declines downwards in all directions towards its circumference, thus following the 
form of the upper surface of the cerebellum. Its inner border is free and concave, 
and leaves in front of it a shield-shaped opening, through which the isthmus encepbali. 
extends. It is attached behind and at the sides by its convex border to the hori- 
zontal part of the crucial ridges of the occipital bone, and there encloses the lateral 
sinuses. Farther forward it is connected with the upper edge of the petrous portion 


of the temporal bone — the superior petrosal sintiB running along this line of attach- 
ment. At the point of the pare petroso, the external and internal borders meet, 
and may be said to intersect each other — the former beinff then continned inwards 
to the posterior, and the latter forwards to the anterior clinoid process. 

The falx cenbslli (folx minor, fi;;. 129, 13) descends from the middle of the 
posterior border of the tentorium, with which it is connected, along the vertical 

1, fall ; 2, superior tongitniiinal ginuB ; 3, concave border of tb« fall ; 4, inferior longitadinal 
siauB ; 5, base of the fali ; 8, straight sioua ; 7. anterior part of the fall ; S, right side of the ten- 
tonutu cer«belli, Been from below ; 9, lateral sinus ; 10, superior petrueal sinue ; 11, inferior petrosal 
dnoa; 12, posterior occipiUl smuH ; 13, faljt cerebelli ; 14, 16, 16, 17, 18, second, third, fonrth, 
tftix, and sixth cranial nerree ; 19, seTenth and eighth nerves; 20, ninth, tentb, and elcTenth 
nerves ; 21, twelfth serve ; 22, 23, lirdt and second cervical nerves ; 24, upper end of the ligamentiun 

ridge named the internal occipital crest towards the foramen magnum, bifarcating 
there into two smaller folds. Its attachment to the bony ridge marks the coarse of 
the occipital sinus or alnnsea. 

StmctTiTe. — The dura mater consists of white fibrous and elastic tissue, arranged 
in bands and laminte, those of the two layers crosBin*; each other obliquely for the 
most part in the cranial dura mater. In the falx and tentorium the bundles 
are arranged radially. It is not uncommon to find the cranial dura mater 
ossified in parts : most commonly in the falx cerebri. In the gptnal dura mater the 
bundles have a nearly longitudinal arrangement. A layer of flattened endothelial 
cells corera its inner surface, and also its outer surface between the places of 
adherence to the bonea and sutnrea. A similar layer of cells also covers both sides 
of the spina! dura mater. The cranial membrane is traversed by numerous blood- 
veseeJs which are chiefly destined for the bones, but there is a wide-meshed capillary 
network with peculiar ampulJary enlargements, distributed near the inner surface of 
the cranial dura mater, and another network near the outer surface. The spaces 
between the fibrous trabeculse contain flattened connective tissue corpuscles which 


frequently have an epithelioid arrangement : these spaces, like those of connectiye 
tissue generally, doubtless serve for the passage of lymph. They can be injected 
from the epiduml space where this exists, and the injecting fluid can be forced along 
them through the thickness of the dura mater into the subdural space. They can 
also be filled by inserting the injecting cannula into the substance of the membrane. 
Minute nervous filaments, derived from the fifth, tenth, and twelfth cranial nerves, 
and from the sympathetic, enter the dura mater of the brain to be distributed 
chiefly to the blood-vessels and to the bone, but partly perhaps to the membrane 
itself. Nervous filaments have likewise been traced into the dura mater of the 
spinal column. 

The arteries of the cranial dura mater are derived from various sources ; the 
principal are three in number, viz., the anterior, derived from the ethmoidal 
branch of the ophthalmic ; the middle, by far the largest, a branch of the internal 
maxillary ; and the posterior meningeal, a branch of the vertebral. There are also 
others derived from the ascending pharyngeal and occipital arteries. Their course 
and relations have already been described (see Vol. II.). Veins accompany these 
arteries, but others, mostly small ones, run independently and open into the venous 
sinuses. One sinus-like vein which accompanies the anterior branch of the middle 
meningeal artery, communicates superiorly with the superior longitudinal sinus, and 
passes inferiorly either into the veins of the orbit, or into the diploic veins, or into 
the sinus cavernosus (Merkel). Communicating with the superior longitudinal 
sinus from its anterior end as far back as the beginning of the occipital region are 
a number of diverticula, from 0*5 to 8 cm. long, which form a series of venous 
lacunse {lacuncB laterales of Key and Eetzius) receiving the independent meningeal 
veins, and some veins from the diploe, and are invaginated by Pacchionian granula- 
tions (see p. 190). These venous lacunsB are not entirely confined to the region of 
the superior sinus, but some may occur in the neighbourhood of other sinuses, 
especially the lateral and straight sinus. 

Subdnral space. — The space between the dura mater and the arachnoid, which 
was formerly, when the latter was considered to be a serous membrane, known 
as the cavity of the arachnoid, is now more usually known under the above title. 
It is in most parts a narrow capillary cleft, containing but very little fluid, which is 
probably of the nature of lymph. Its contained fluid finds exit chiefly around the 
arachnoid villi (Pacchionian granulations) into the sinuses of the dura mater, but 
partly by way of the- lymph-clefts in the sheaths of the issuing nerves, cranial and 
spinal (Key and Betzius). In animals it has been shown (by Schwalbe) that the 
space is also in communication with the deep lymphatic vessels and glands of the 
neck and loin. Coloured fluids injected into the subdural space are never found to 
pass into the subarachnoid space, the arachnoidal limiting membrane being every- 
where a closed one. Nevertheless, coloured fluids can be made to pass from the 
subarachnoid space through the arachnoid villi into the prolongations of the 
subdural space which surround those villi within the venous sinuses and lacunse, 
and thence into the sinuses themselves. This passage may, however, take place by 


The pia mater is a delicate, fibrous, and highly vascular membrane, which 
immediately invests the brain and spinal cord. 

Upon the hemispheres of the brain it is applied to the entire cortical surface of 
the convolutions, and dips into all the sulci, most of which thus contaiti a double 
layer. From its internal surface numerous small vessels pass into the substance of 
the brain, and hence this inner surface is very flocculent, and is named iamentum 
cwebri. On the cerebellum a similar arrangement exists, but the membrane is finer. 


and the doable fold only distinct in the larger sulci. The pia mater also at the 
transverae fissure is invaginated into the lateral ventricles and over the third 
^ ventricle (covered however by the epithelium of those cavities), and there forms the 
velum interpositum or tela choroidea superior and choroid plexuses. It is also 
prolonged over the posterior wall or roof of the fourth ventricle, where it forms the 
Bo-called tela choroidea inferior and choroid plexuses of that ventricle. 

The Tslimi iatarpovitnm, or t«lA dioroidsa anparior, is a triangular fold 
of pia mater, between the two layers of which orachDoidal tissue and blood-vessels 
are contained, which lies immediately underneath the fornix, and can therefore only 
be properly seen when this strncture is cat throngh and raised (aa in fig. 130). The 
velum interpositum is then seen to cover in the third ventricle and to extend over 

Fig. 130.— Viiw or ihi upwrn bde- 

MBIATi (from Sappej aftw Vieq- 

d'Aiyr). I 
1, foiB-p&rt of the teU choroiden 
or Telom interpagituni ; 2, '2, choroid 
pleius J 3, S, left veio of (iaieo parti; 
uO'ereJ bj the right; i, interior 
pillttn of the fornix diTidad in front 
of the fonunen of Monro ; on either 
■ide ira leea small veins from tbo 
front of the corpus caLosom and the 
leptum lucidum ; 5, rein of the 
corpuB atriatiim ; 6, convoluted 
mtfgin&l vein of the choroid plexue ; 
7, vein rising from the'tbahuDus opti. 
cua and corpus striatum ; 8, vein 
proceeding from the inferior comu 
and hippocampns major ; y, one from 
the poeterior comu; 11, fornix 
divided ne&r its middle and turned 
backwards ; 12, lyn ; 13, posterior i 
pillar of the fornix ; 14, the splenium , 
of the corpus calloenm. 

the adjacent npper sarface of 
the optic thalamus on each 
side as far as the oblique 
groove which marks that sur- 
face (p. 110, and fig. 82). 
The base of the triangle is 

continuous with the general pin mater at the back and sides of the brain, the apex 
ends just behind the anterior pillars of the fornix (at the foramen of Monro). Each 
side of the triangle is bordered by a choroidal plexus which projects from under the 
edge of the fornix into the respective lateral ventricle ; behind, these plexuses are 
continued along the mesial border of the descending cornn of the ventricle, where 
they are inv^inated into the choroidal fissure, projecting over the fimbria ; in front 
they converge, becoming gradually smaller, to the foramina of Monro, between 
which they become united. From this united part two other smaller plexnsea pass 
backwards along the under surface of the velam interpositum, close to the middle 
line in front, but diverging behind (choroid plexuses of the third ventricle). 

The choroid plexuses are covered where they project into the cavities by the 
epithelium of the ventricles, as is also that part of the velum interpositum which 
roofs in the third ventricle. Along the choroid plexuses a prominent vein, the 
choroid vein (fig. 89, p. 125), courses from behind forwards to join the vein of the 
corpns striatum and form the corresponding vein of Galen at the foramen of Monn> : 


the two veins of Galen pass forwards from this point in the middle of the velum 
interpositum, diverging somewhat behind, but again converging and ultimately 
becoming united into a common trunk {vena magna Galenic fig. 130, a) which opens 
into the straight sinus. In this coarse they receive several tributaries from the 
optic thalami and other parts. 

Tela choroidea inferior. — This name has been given to the layer of pia mater 
which, prolonged from the medulla oblongata, overlies the inferior half of the fourth 
ventricle and is reflected at the margin of the velum meduUare inferius on to the under 
surface of the cerebellum. Like the velum interpositum, this also hafl two sets of 
choroid plexuses, mesial and lateral, which are continuous with one another in front. 
The mesial plexus extends forwards along either side of the middle line from the 
foramen of Majendie (p. 188) to where the tela is reflected along the edge of the 
inferior medullary velum ; here the mesial plexuses are continued into the lateral 
plexuses on either side, and these extend to the apertures (in the pia mater) of the 
lateral recesses of the ventricle (p. 48). 

On the spinal cord the pia mater has a very different character from that which 
it presents on the cncephalon, so that it has even been described by some as a 
different membrane under the name neurilemma of the cord. It is thicker, firmer, 
less vascular, and more adherent to the subjacent nervous matter : its greater 
strength is owing to an external fibrous layer, which is arranged in longitudinal 
glistening bundles. A fold of this membrane dips down into the anterior fissure of 
the cord, and serves to conduct blood-vessels into that part. A thinner process 
passes into the greater part of the posterior fissure. At the roots of the nerves, both 
in the spine and in the cranium, the pia mater becomes continuous with their 
connective tissue sheaths. 

The pia mater of the cord is thickened by a conspicuous fibrous band, running 
down in front over the anterior median fissure. This was named by Haller, Imea 

Structure. — The pia mater of the cord consists of two layers, the outer one 
being composed of interlaced bundles of connective tissue, which are for the most 
part parallel and longitudinal, and the inner or intima of peculiar stiff bundles 
bending suddenly and enclosing somewhat angular interspaces. Both surfaces of 
this inner layer are covered with endothelial cells, and there is a network of fine 
elastic fibres near the sui^faces. On the cord pigmented cells are sometimes scattered 
among the elastic fibres. The outer and inner layers are separated here and there 
by cleft-like lymphatic spaces communicating on the one hand with the subarachnoid 
space and on the other with the perivascular canals immediately to be mentioned. 
In the pia mater of the brain only the inner of the two layers of the pia mater of 
the cord is represented. 

The choroid plexuses are beset with a large number of highly vascular 
villous prolongations of the pia mater (choroidal villi), the larger of which are from 
1 mm. to 2 mm. long, but are subdivided into smidler secondary or even tertiary 
villi. Each larger villus has an afferent artery and efferent vein which open into a 
capillary network lying close to the surface. The free surface of the villi and of the 
depressions between them is covered everywhere by a simple flattened or cubical 
epithelium, which is ciliated in lower vertebrates, but in mammals is said to possess 
cilia only in embryonic life. Each cell very commonly contains a yellowish fat 

The pia mater contains great numbers of blood-vessels, which subdivide in it 
before they enter the nervous substance. In the pia mater of the cord they lie 
between its two layers, but in that of the brain on the surface of the membrane, 
either projecting freely or covered by subarachnoid trafeeculae. Further each vessel 
is enclosed by a sheath composed of a more dense arrangement of the fibres of the 


metnbi-ane (perivascnlat sheath). The diameter of the (lymphatic) canal thus 
fonned may be consideiably larger than that of the contained veBsel. A similar 
sheath, derived fh)m the pia mater, accompanieB the vessel into the suhstance of the 
brain. At its commencement it is loose and funnel-shaped and can be injected from 
the subarachnoid cavity. On the cerebrum the inner layer of the pia mater is more 
closely adherent to the cortical suhstance of the convolutions, than on the carebellnm, 
where a distinct space traversed by fibres exists between the two. 

XTsrvea. — Purkinje described a retiform arrangement of fine nerve-fibrca in 
the pia mater ; these are derived, according to Kolliker and others, from the 
sympathetic, and from the third, fifth, sixth, facial, pneumogastric, glossopharyngeal, 
and accessory nerves. Most of the fibrcs are destined in all probability for the 

The spinal pia mater is supplied by nerves from the grey rami commnnicant«a of 
the sympathetic. 

Tox AiULOHKOis mumbrahi:. 

The arachnoid is a delicate membrane whk'h is situated outside the pia mater, 
and invests the brain and spinal cord much less closely than that membrane. It 
passes over the varioQa eminences and depressions on the cerebrum and cerebellum, 

Fig. 131.— Seotiob of thb ros- 

run VKNTBitLKa. (After Key 

aDd Reuius.) 

The Bcction was nisile in the 

frozen itate, the cavitiea haring 

been previouBl; Gllud with injec- 

1, I', atlKS vertebra ; 2, odon- 
toid proceBs of the axis, 2' ; 3, 
third leatricla ; i, fourth v«btri- 
clo ; C. V, corpnii callosum ; C, 
gyrus foniicatus ; C, cerebellum ; 
t, t«nt')rum ; p, pituitary bod; ; 
c.c, central i^anal of the coH ; 
/.if, in the cerebello-mednllarj 
port of tbt Bubarachnoid space, ie 
close to the focamen of Magendie 
by which that space comnmnicales 
with the fourth veatriole. 

without dipping down into 
the sulci and smaller 
grooves. Beneath it, be- 
tween it and the pia mater, is a spac« (subarachnoid space) In which is a considerable 
quantity of fluid (subarachnoid fluid), and in which are seen the larger blood-vesselB 
passing obliquely towards the brain. 

The sabaxaduioid apwie is larger and more evident in some places than in 
others. Thus, in the longitudinal fissure, the arachnoid does not descend to the 
bottom, but passes across, immediately below the edge of the falx, at some distcmce 
above the corpus callosum. In the interval thus left, the arteries of the corpus 
callosum mn backwards along that body. At the base of the brain and in the 
spinal canal there is a wide interval between the arachnoid and the pia mater. In 
the base of the brain, this subarachnoid space extends in front over the pons and 
the interpeduncular recess as far forwards as the optic nerves, and behind it forms 


a considerable interval between tbe cerebellum and the back of the medalla 
oblongata (fig, 131). In the spinal canal, where it surrounds the cord, it is of 
considerable extent. It is occupied, in both brain and cord, by trabeculss and thin 
membranous extensions of delicate connective tissue, connected on the one hand 
with the arachnoid, and on the other with the pia mater. This tissue is most 
abundant where the space between the two membranes is least. It is dense in the 
neighbourhood of the vessels, and is continuous with the tissue of their walls. In 
several places therefore the arachnoid is separated bj larger intervals than at other 
parts from the pia mater. 

The Bpaces which are thereby produced are termed ciiterrus arachnoidales (reeenroirs of 
subarachnoid fluid). They have been studied especially by Key and Retzins, and by Dnret. 
The principal are situated at the base of the brain. The largest {cistema cerehell<MnedvHarii) 
lies between the middle part of the cerebellum and the medulla oblongata, and is directly 
continued from the subarachnoid space of the cord. Others lie in front and at the sides of 
the medulla oblongata and pons {c. pontes media s. baHlarU and a, jwiitu late^ralU^y below the 
interpeduncular space (c. irUerpeduncularis)^ over the cerebral peduncles (fi.c, peHpeduncularei), 
behind the optic chiasma {c, chicumatW), in front of the chiasma {c. laminte c%nerefp\ in the 
fos8» Sylvii (c.c.fo9t(B Sylvii)^ and over the corpus callosum {c, corporis callosi). These are 
all in free communication with one another, being only partly separated by imperfect septa of 
arachnoid tissue. They reoeive the subarachnoid clefts (Jtnmina) which follow the course of 
the great fissures (Rolandic, Sylvian, parallel, &c.), and which themselves receive the clefts 
which follow the course of the secondary and tertiary fissures (rivi and riruli of Duret). 

The subarachnoid space communicates with the ventricles of the brain by means 
of the foramen of Magendie (fig. 181, /Jtf"), an opening into the lower part of the 
fourth ventricle, through the pia-matral expansion (tela choroidea inferior) which 
covers the ventricle ; through apertures in the lateral recesses, one on each side, 
behind the upper roots of the glossopharyngeal nerve, in the pouch-like extension 
of the membrane beneath the flocculus ; and perhaps also at the clefts described by 
Merkel in the descending cornua of the lateral ventricles (see p. 126). 

The cerebro-spinal fluid is lodged in the subarachnoid space in the meshes of 
the trabecular tissue, and since this space communicates with the ventricles of the 
brain, the fluid within these must be regarded as of the same nature. It differs 
in many respects from ordinary lymph (compare Halliburton, Cerebrospinal Fluid, 
Journal of Physiology, Vol. X.). 

The spinal subarachnoid space (fig. 182, A;, I) is divided by an imperfect fibrous 
septum on either side termed the ligamentum denticulatum (^) into anterior and 
posterior portions. As was pointed out by Magendie there also exist a sort of septum 
dividing the subarachnoid space at the back of the cord (septum posticum) (<;), the 
relations of which have been carefully studied by Axel Key and G. Retzius. It is a thin 
membranous pai*t]tion, which passes in the median plane from the pia mater covering 
the posterior median fissure of the cord to the opposite part of the loose portion of 
the arachnoid membrane. It is most perfect in the cervical I'egion, being incomplete 
below. It consists of numerous fine lamellae, enclosing between them small spaces, 
within which run the larger blood-vessels. Subarachnoid trabecules also connect the 
nerve-roots with the inner surface of the arachnoid, and in the dorsal region fine 
membranous trabecule extend between the posterior nerve-roots and the posterior 
septum. In most parts however the subarachnoid trabeculae are far less developed in 
the spinal canal than in the cranium. 

The nerves as they pass from the brain and spinal cord receive their perineural 
covering from the pia mater, and, in addition, two looser sheaths, an outer from the 
dura mater, and an inner from the arachnoid (tig. 128). Upon the optic nerve 
these sheaths remain distinct and separate, so that the space which each encloses 
may be injected, the outer from the subdural, tbe inner from the sub-arachnoid space. 
On the other nerves the arachnoidal sheath soon ceases, and the single sheath eventually 


blends with both the epineurium and perineurium of the nerves. Acoordinglj it is 
found that injection driven into either the subdural or the subarachnoid space passes 
readily along the nerves even as far as the limbs. There thus exists a continuity 
between the ventricles of the brain, the subarachnoid space^ and the lymphatic 
spaces within the nerve-sheaths. 

Structure.— When examined under the microscope, the arachnoid membrane is 
found to consist of distinct riband-like bundles of fine fibrous tissue interlaced with 
one another. The intervals between these bundles are filled up by delicate 
membranes, composed of expanded cells, the nuclei of which persist and are scattered 
over the structure, Several layers of this tissue, arranged in a complex way, 

Fig. 132. — Section op thb spinal cord 


DORSAL region). (Key and Eetzius. ) 

a, dura mater ; b, arachnoid ; c, sep- 
tum posticum ; dj e, f, subarachnoid 
trabecal», thoHe at /, /, supporting bun- 
dles of a posterior nerve-root ; g^ liga- 
mentiim denticulatum ; h, sections of 
bundles of an anterior nenre-root ; k, I, 
subarachnoid space. 

constitute the arachnoid mem- 
brane proper. The subarachnoid 
trabeculse consist of bundles of 
similar fine fibrillar tissue, each 
of which is surrounded by a deli- 
cate nucleated sheath, also com- 
posed of cells, and continuous 
with the intertrabecular cell- 
membranes of the arachnoid itself. The finer trabeculae when swollen by acetic 
acid very frequently show the well-known ring-like constrictions. The subarachnoid 
membranous expansions have a similar structure. In the spinal arachnoid the 
fibril-bundles have for the most part a longitudinal direction. 

Volkmann described a rich plexus of nerves in the arachnoid membrane of 
certain ruminants. Kolliker failed to detect their presence ; but they have been 
again described by Bochdalek, who traces them to the portio minor of the fifth, the 
facial, and accessory nerves ; and they have likewise been followed by Luschka. 

Ligamantmn denticolatum. — This is a narrow fibrous band which runs along 
each side of the spinal cord in the subarachnoid space, between the anterior and 
posterior roots of the nerves, commencing above at the foramen magnum, and 
reaching down to the lower pointed end of the cord (fig. 183, 9, and fig. 182, g). 
By its inner edge this band is connected with the pia mater of the cord, while its 
outer margin is widely denticulated ; its denticulations are attached by their points 
to the inner surface of the dura mater, and thus serve to support the cord along 
the sides, and to maintain it in the middle of the cavity. The first or highest 
denticulation is fixed opposite the margin of the foramen magnum, between the 
vertebral artery and the hypoglossal nerve (shown in fig. 182 of Vol. II.) ; the others 
follow in order, alternating with the successive pairs of spinal nerves. In all, there 
are about twenty-one of these points of insertion, but the lower six or seven arc less 
regular. The points of the lower denticulations are prolonged into threads, and 
ascend slightly to their attachments. At the lower end, the ligamentum denticu- 
latum may be regarded as continued into the terminal filament of the spinal cord, 
which thus connects it to the dura mater at the extremity of the sheath. The free 
edge, in the intervals between the denticulations, is slightly thickened, and in many 


partH is oloeelj applied to the iirner Eurface of the BTachnoid, with which it is often 
directly connected by fine trabecute. The denticulationB do not perforate the 
arachnoid but receive from it fonnel-ehaped sheaths, which accompany them to the 
inner snr&ce of the dura mater (Asel Key and Ketzius). 

In strncture the ligament consists of white fibrous tissue, mixed with many 
exceedingly fine elastic fibres. Several layers of fine connective tissue trabecolffi 
may be traced ; they are surrounded by sheaths, which are composed of delicate 

Fig. 1S3.— View »oa behiiid of th( viDii 

(Sappej.) j. 
The dunt-nuitral >hBBt]] hu been opened bj s medi&n incision and is atretched to either side. In 
the npper and middle paTta(AandB)the poBleriorDerfe-rootB have been removed to ahow the ligamentnm 
ilenticulatain. 1, fourth ventricle ; 2, 3, i, cerebellar pedoncles ; G, claviu ; 6, T, 8, rooti of glmso- 
pharjngeal, vagiii, and taxsaor/ nerves ; 9, pointa of ligamentam denticnlatnm ; 10, line of entnnce of 
poaterioi loota into ipinal cord i 11 (in b), posterior median fiseore; 12, ganglia; 13, cnt anteriar Toota ; 
14, mixed nerve ; 15, Ifl, filam temiinale ; 17, cauda equina. 

nucleated cells, and here and there espand into membranes. Its tisane is continuous 
on the one hand with that of the pia mater, and at the apices of the denticnlationg 
with that of the dura mater. 

Olaudnln PaooUoiiii or aradknoidal villi. — Upon the external surfiice of the 
dura mater, in the vicinity of the longitudinal sinus, are seen numerous small pnlpy 
looking elevations, generally collected into clusters, named glands of Paccbioai 
(fig. 134). The inner surface of the calvaria is marked by little pits, which 
receive these prominences. Similar excrescences are seen on the internal surface of 
the dura mater, and npon the pia mater on each side of the longitudinal sinus, and 
also projecting into the interior of that sinus (a). Occasionally tbey are found 
also in other gituations. 

On a careful examination of the connections of these bodies it will be found that 


the elevations found on the onter surface of the dara mater and n-ithin the 
longitndinal Binua, in no instance take origin in those positions, but that they are 
gtape-like bodies which are attached more deeply, and in their groirth have 
invaginated the dura mater. Their precise origin and nature were long the subject 
of conflicting opiuious, but it has been satisfactorily shown by Luschka that they arc 
villi of the arachnoid. On each side of the sinus, and communicating with it, are 
large venous spaces in the dnra mater (lacunoe lateraleB, see p. 184) ; into these the 
villi project even in new-bom animals, and those which appear to perforate the data 

Kg. 134.— Skctiok oy tat urPFB paki or thk bsuv , 

THE iHiCHNoimi, VILLI. (Kej and Rfitiius.) Magnified. 

c.e., corpag callosam ; /, fall cerebri ; a.o., Eubarachnoid Bpoce, perraded b; a netirork of 6ne 
trabeculas ; from it the fungiform rilli are seen projecting into the latenit lacuns o[ the dura mater. 
Some are projecting into the laperior longitudinal Bious, i. 

mater and appear ou the surface have their inner parts in these spaces. Each vilhis 
is covered by a membrane, continuous with the arachnoid. Outside this is another 
fine membranous sheath, derived from the dura mater, and the interval between the 
two is continuous with the subdnral space. Within the villus is a spongy trabecnlar 
tissue, continuous with the subarachnoid tissue, and of similar structure (Key and 

Fluid injected into the subarachnoid space passes freely into the Pacchionian 
bodies, and is fonnd after a time to filter through their walls and thus to get into 
the subdnral space, although there does not appear to be any open communication 
between the interior of these bodies and the prolongation of the subdnral space 
which snrronnds them. Moreover, if the injection is continued it can be driven 
even into the interior of the venous sinuses and lacunte which are found in connection 
with them, especially into the superior longitudinal sinus, into which the arachnoidal 
villi project. So that these villi seem to afford a means of passage of the cerebro- 
spinal fluid from the subarachnoid space into the venous sinnses, when the fluid 
preesnre in the subarachnoid space becomes from any cause increased above 
the normal. 


Blood supply of tk« gpiunl cord. — The arteries of the spinal cord are (I) the 
anterior spinal, double above where it is derived from the vertebrals, but single and 
median below where it is reinforced by a series of small vessels derived from the 
vertebral, intercostal, lumbar, and other arteries, and passing to the cord along 


the anterior roots, and (2) the jtaind potUrior ^inal arteries, similarly derived from 
the vertebmls, intercoatals, and other arteries, and mnning jnst in front of the line 
of attachment of the posterior roots. Another small longitudinal anastomotic chain 
formed by branches of the posterior spinal runs alon^ just behind the line of the 
posterior roots.' The branches of these vessels ramify ia the pia Diater inventing the 
cord, communicating with one another to form transverse anastomoses, and from the 
main vesBeU and their ramifications vessels pass in to supply both the grey and 
white Bubstauce. 

The small entering branches may be described as forming two systems, a 
centrifugal and a centripetal. The first is composed of a series of arterioles, 
{central arterioles, Soss), 200 to 300 in number, which pass from the anterior spinal 

Fig. 135. — SEHiDuaKiMHiTia BipusiirriTtoy 


steiasr. ) 
a.i.a., anterior Bpinal laterj ; c, a, ceaUai 
arteriole ; a, an anutomotic branch anitiiiE it 
with another arteriole of an adjacent legment ; 
CL, branch to Clarke's column; ci.p^., artery 
of posterior flBSure ; p.m.a., postenor meaiiU 
arteij; a.p.c, artery of posterior cnrau j p.:a., 
branch of posterior apinal arter; puaing iato 
gelaUaons eubstance ; p, other ]ieriphera] or 
centripetal aiierioleB paaaiog through wbito 
■nbatance of cord. 

artery into the anterior median fiaanre, 
penetrating to the anterior commissare. 
Here each one passes either to the right 
or left, and divides into smaller arteries 
and capillaries for the central parts of 
the corresponding crescent of grey 
matter; bnt a considerable ascending 
and descending ramuscule is also given 
off, and these overlap in their distri- 
bution the corresponding longitudinal 
branchee of the adjacent central arte- 
rioles. Although mainly distributed to the central parts of the grey matter the 
central arterioles may also send branches to join the capillaries of the white matter. 
The second or centripetal set has a convei^ing or radial arrangement, passing in 
from the periphery. Some of these simply form capillary loops, which supply the 
superficial layers of the cord. Others are distributed to the white matter, where they 
form comparatively large-meshed longitudinal plemses. But the most considerable 
of the centripetal arteries penetrate to the grey matter, and pour their blood into the 
close capillary network which pervades it, supplying the parts not served by the 
centrifugal vessels. The capillaries of the Bubstantia gelatinosa are less nnmerons 
than in the rest of the grey matter, and their meshes are mostly longitudinal 

Special mention may be made of a series of small median arterial branches which 
enter the posterior fissure, penetrating in it to the posterior commissure, and giving 
off branches which supply the adjacent parts of the posterior white columns and 
Clarke's column, where this is found ; and of the vessels which enter the grey matter 
with the bundles of the anterior and posterior nerve-rootB, and are distribnted to the 
correspondiug comua. It would appear however that no one part is supplied by only 
one set of arterioles, nor is any one set of arterioles confined in its dietribution to 
' For the origin and coune of tie ipinal arteriea ie« Vol. 11., pp. 431 and 4S2. 


any oae white column or group of cells in the grey matter. At the same time it 
should be noted that within the cord itself (as within the brain), all the arteries are 
'' terminal arteries," in Cohnheim's sense, that is to say, they do not anastomose with 
other arteries, but each one terminates in its own capillary area, and supplies no 
other. There is however much yariation in the extent of the capillary area supplied 
by any of the arterial branches, and no definite statement can be made concerning 
the exact region supplied by any set of arterioles (Eadyi). 

The origin and course of the veins of the spinal cord have been described 
in Vol II., pp. 533, 534. The most considerable are two longitudinal median 
vessels, one running along the anterior median fissure along with the anterior spinal 
arteiy, and another over the posterior median fissure, unaccompanied by any 
considerable artery. Both of these median veins have a tortuous course, and the 
posterior one is frequently broken up into a kind of venous plexus, with longitudinal 
meshes, which extends over the whole posterior surface of the cord. There is also 
a less perfect lateral anastomotic chain lying behind the line of exit of the anterior 
nerve roots. All these vessels communicate freely with one another by lateral offsets. 
They receive the venous blood from the cord on the one hand, and on the other hand 
carry it away by veins which accompany, at frequent intervals, the nerve roots. In 
the upper part they join the veins of the cerebellum and pons, and ,the venous 
sinuses around the foramen magnum. Within the cord their branches anastomose 
frequently. The vein accompanying the anterior spinal artery receives, like that 
vessel, very numerous tributaries from the anterior median fissure (central venules) : 
these carry away a large part of the blood from the grey matter; the peripheral 
venules, which enter the veins of the pia mater which covers the general 
surface of the cord, chiefly carry away the blood from the capillaries of the white 

Blood-supply of the brain. — The origin and course of the vessels which supply 
the brain have already been described in the section Angeiology, Vol. II. pp. 411 to 
415 (arteries), and 519 to 524 (veins). In passing to their distribution the several 
arteries, having passed across the subdural space, enter the subarachnoid space and 
then divide and subdivide into branches, which, in their further ramification on the 
nervous centres, are supported by the pia mater, and, it may be remarked, are more 
deeply placed in the various fissures and sulci than the small veins, which do not 
accompany the arteries, but pursue a different course, and are chiefly seen upon the 
surface of the pia mater. From the arteries in the pia mater of the hemispheres 
very numerous small branches pass vertically into the grey matter of the convolutions. 
Most of these {cortical arteries) at once break up into a close plexus of capillaries for 
the grey matter ; but others (medullary arteries)^ larger but less numerous, pass 
through the grey matter, giving off only a few small branches to it, and penetrate 
for some distance into the medullary centre, where they divide into a long-meshed 
capillary network. The smaller branches of arteries anastomose together to a 
certain extent in the pia mater before penetrating into the superficial grey matter 
(Huebner), but the branches which pass to the chief ganglia, such as the optic 
thalamus or corpus striatum, do not anastomose with one another. 

Moreover, it is to be observed that, whilst the main branches of the arteries are 

situated at the base of the brain, the principal veins tend towards the upper surface 

of the hemispheres, where they enter the superior longitudinal sinus, most of them 

looping 'forwards as they pass into the sinus, and often entering the dura mater 

a short distance from the sinus, but more usually having a free course, sometimes 

of considerable length, through the subarachnoid space in passing from the pia into 

the dura mater. The veins of Galen, coming from the lateral ventricles and choroid 

plexuses, run backwards to the straight sinus, in the subarachnoid tissue which lies 

between the two layers of the velum interpositum. 

VOL. in. o 

It may be convenient here to recapitalate the sonrces of the blood supply to the 
seven] parts of the encephalon. 

The medulla oltlon^ts »nd pou Varolii are supplied by branches from the 

Fig. 136.— TBI uniiin or tbi bui or thk ouuidm. (Q. D. T., after Dnret, and from ubira.} 

Od tbe left lide of the bnin the temporal lobe ia cut tfa.j so u to opeo the interiar and poaterior 
horua of the lateral Tentride. The mid-bnio u dirided cloie above tlie pons and the poaterior e«i«bral 
Aiierisa are eat nt their origin from the basilar. 

CeTttnU arteriei (to the basal ganglia) : am, antero-mesial groap ariiing from tbe anterior cerebral ; 
lU, antero- lateral group, from the middle rercbral ; pm, pi (on the optio tbalamue), poetero-meaia] and 
poiftero-lateral gronpa, from the posterior cerebral. 

Choroidal arttrin : a ck, anterior, from the intemal carotid ; p cA (dd tbe iplenium), poaterior, from 
the posterior cerebral. 

Peripheral arterUi; 1,1, inferior internal frontal, from tho anterior eorebml ; 2, inferior eileraal 
frontal ; 3, ascending frontal ; 4, nacending parietal, and 5, temporo-parietal, from tbe middle oerebrml ; 
6, anterior temporal, 7, poaterior temporal, and S, occipital, from tbe poeteiior cersbnl. 

anterior epiaal, the vertebral, the baailor, and tbe posterior cerebral arteries. The 
branches enter the pons and medulla oblongata in two set«, lateral or radicular 


(following the roots of the nerves), and median,— the latter passing in the nphe 
to the grej matter on the posterior surface. The valve of Yieussens and the 
Bnperior pednncle of the oerebellam receive twigs from the superior cerebellar 
arteries. The choroid plexuses of the fonrth ventricle are supplied by the inferior 
cerebellar arteries. 

CcMbdlnm.— The under surface is supplied by the inferior cerebellar arteries 
from the vertebral, and the anterior from the basilar. The upper aurface is supplied 
chiefly by the superior cerebellar arteries from the basilar : its posterior portion 
from the inferior cerebellar. 

The omrft cerebri derive their blood supply from the posterior communicating 
and the posterior cerebral arteries. Branches of the latter, and also others from the 
end of the basilar, enter the posterior perforated space. 

The corpora qoadrigsnmia and corpora gooicnlata are both supplied by the 
posterior cerebral artery, but branches of the superior cerebellar arteries pass to the 
inferior corpora quadrigemina. 

The optic thalamaa is supplied above and on the outer, inner and posterior 

Fig. 187.— CoMioiL DiataiBOtiOH o» thb mibbi-i ck&ubkal iRiiai. (0. D. T., after Cbucot.) 
OHT., anlcro-latAntl groap ol central arteries : 

sidta by branches of the posterior cerebral artery, but its anterior and inner 
portion receives twigs from the posterior communicating arieries of the circle of 
Willis and its anterior and outer portion from the middit: cerebruL 

Cerebral ^maiMjibiBxtm.— Frontal lobe. — Tht superior frontal and anterior two- 
thirds of the middle frontal convoliiLion, with the upper extremity of the ascendiqg 
frontal, are supplied by the anterior cerebral. The inferior frontal convolution, the 
posterior extremity of the middle frontal, and the greater part of the ascending 
frontal oonvolutiona are supplied by the middle cerebral. The orbital surface is 
Bupplied, outside the orbital sulcus, by the middle cerebral : within that buIoob 
(including the olfactory bulb) by Lbe anterior cerebral. 

Parvtal lobe. — All the convolutions of the parietal lobe are usually supplied 
by the middle cerebral artery. 

Occipital lobe. — This lobe is supplied entirely by the posterior cerebral artery. 

Ten^wdl lobe. — The snperior and upper parts of the middle temporal oonvo- 

Fig. 13S. — DuoiuMs BHawiNo the akeib or oohtioal disthibdtioii o 

A, Utonl ; B, meaial aspect ; o, basal tapect. 
Tbe area aupplied by the middle cerebral freqaentlj extends to the upper border of the fa 
u Ui« regioB of the parietal lobe, and tberetore winievliat further thiHJ is rspresealed in A . 


lotions are sapplied by the middle cerebral artery. The lower portion of the lobe 
by the posterior cerebral. 

Inner surface of the hemispheres. — The whole anterior and upper portion, aa far 
back as the parieto-occipital fiasnre, is supplied by the anterior cerebral artery ; the 
cnneate lobule and the occipito-temporal region by the posterior cerebral. 

The distribution of arteries to the several parts of tlie cerebral cortex is 
illnetrated in the accompanying digrams (fig. 138). 

The corpus callosum is chiefly supplied by the anterior cerebral. 

The ffretf substance at Ihe base of the cerebrum is supplied by Bmall twigs from 
the adjacent vessels of the circle of Willis, or from the roots of the cerebral 
vesaels which pass off from the anastomosis. 

Central parts — corpus striatum. — Both nucleus caudatus and nucleus lenticnlaris 

are supplied almost exclaBively by the middle cerebral artery, the numerous branches 
to these parts entering through the foramina in the anterior perforated space 
(fig. 136). They are divided by Duret into lenticular, lenticulo-siriaie, and lentKulo- 
optic (lenticulo- thalamic). These pass directly to their destination without anasto- 
mosing with one another, and traverse the zones of the lenticular nucleus and the 
internal capsule, to terminate finally in the caudate nucleus and optic thalamus 
(fig. 139). One in particular of the lenticnlo-striate arteries which passes through 
the outer part of the putamen is very frequently the seat of hemorrhage, and 
it has accordingly been termed by Charcot the " artery of cerebral hemorrhage " 
(fig. 139, x). 
The anterior part of the caudate nucleus is also supplied by the anterior cerebral, 


and its npper surface receives line twigs from the lateral choroidal branch of the 
pofiterior cerebral. 

The choroid plexuse$ of the laieral ventricUs are supplied (1) by the anterior 
choroid branch of the internal carotid which passea obliquely backwarde and ont- 
wards, and enters the choroid plexuB at the anterior end of the descending oomn, 
supplying two-thirds of the plexus of the lateral ventricle ; (2) by the poatero- 
latend choroid artery, a branch of the posterior cerebial, which supplies the 
remaining third of the plexus. The choroid plextia of the third vmtricU is 
supplied by a branch (post«ro- mesial) of the posterior cerebral. The veltan 

Fig. 139. — Frohtai sictioh or tse bkatn, anowiRa tbs mode or OBiaiF 


c.e., corpus cuUosnm ; fo., fornix ; a.c, Bnt«rior commigBurn ; a, corpus albicanii ; i, infnndibnliiin ; 
ch., cbUinia ; It., optic tract ; v.l., Uteral Tentricle ; n.c, nucUuB caudntus ; n.l., nocJeus leotica- 
luris ; Oi., tbalmuue ; c.i., int«niBl capsule ; d., clsustrum ; am., nucleus smjgdalK ; sboTS v, tx^trj 
at hsmorrhsgc. (The ploD of the section is copied from Merkei. ) 

interpoailum is also supplied by the two last-named branches of the posterior 
cerebral. The parls in the quadrilateral spate at the base of the brain including 
the chiasma, the infundibulum and the corpora mamillaria receive branches directly 
from the circle of Willis, 

For further details on the subject, which derives importance from the relation 
of different local pathological conditions to the vascular distribution, the reader is 
referred to a series of articles by Duret in the Archives de Physiologic for 1873 and 
1874, to a paper by Huebner in the Med. Centralblatt, 1872 ; and to a work 
entitled " Die luetische Erkranknng der Hirnarterien," Leipzig, 1874, by the same 

XTinpli-psitbB of the br&ln and apliud card. — Neither the brain nor the Bpioal cord 
poBsecaes tnie lymphatic vessels. The lymph finds its way ont of these orgMiB by means of 
periTBscDlar spaces in the tunica adventitia of the blood-vewels ; these perivsacnlar eptoem 
oonunnnioate with the Bnbaischnoid space at the surface of the biain and coid (Key and ReUius). 




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Hoeel (u. Flechsiflr), Die Centralwindungen ein Centredorgan der Hinterstrdnge, NeuroL 
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Iianflrley and Qriinbauni, On the degenerations resulting from removal of the cerebral cortex and 
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Luyv, Nouvelles recherehes sur la structure du cei-veauet agencement des fibres blanches c^ribraUs, 
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PopofT, Zur Frage vom Ursprungsgebiete der Fasem der vorderen Commissur, Neurol. Centralbl., 

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Sherrington, Nerve tracts degenerating secondarily to lesions of the cortex cerebri^ Joum. 
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Zaoher, Beitr. z. Kenntniss des Faservetiaufs im Pes Peduneuli, sow. it. d. corticalen Beziehungen 
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Znckerkandl, Ue. d. BiecKbundd des Comu Ammonis, Anat. Anzeiger, iii., 1888. 


Berkley, H. J., The meduUated cortical fibres, Ac., Medical Record, New York, 1892. 

Bets, Ueber diefeinere Struktur d. menschl. Gehimrinde, Med. Centralbl., 1881. 

Blumenau, Ii., Zur Entvnckl. u. feineren Anatomic des Bimbalkens, Arch. f. mikr. Anat., 

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los batracios reptiles y aves, Trabajos del laboratorio histologico, Barcelona, 1891 ; Sur la structure de 
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Conil, O., Des risuUals obtenus par la mithode de Golgi appliquie d Vitude du bulbe olfactif, M^m. 

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Bzner, Zur Kenntniss vom feineren Bau der Grosshimrinde, Wiener Sitzungsb., Bd. 88, 1881. 

Gtoliuchten, v., et Martin, Le bulbe olfactif chez guelques mammifires. La Cellule, t. Tii., 1892. 

Gtolffi, Sulla fina strvUura d. btdbi olfattori, 1876 ; Origine du tractus olfactorius et structure 
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sistema nervosa, Kiyista sperim. di freuiatria, 1883. 


Kolllker, v., Ut. d, ftineren Ban des Bulbus oJfactortus, Sitzungsb. d. Wttnbiiig pli78.-iDed. 
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Major, H. C, Histology cf the Idand of Reif, West Biding Asylum med. Beports, vol. vi. ; and 
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Meynert, Th., Article " Brain,'' in Strickei-'s Bistology, 1872. 

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Sala, L., Zur feineren Anatomic des grossen Seepferdefusses, Zeitsch. f. wiss. Zool., Bd. 52, 
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Sohaffer, K., Beitrag zur ffistologie der Ammonshornformation, Arch. f. mikr.Anat., xxxix., 1892. 

Bpltzka, E. O., Article ** Brain, Histology," Bef. Handbook of the Medical Sciences, viii., 1889. 

Valpius, O., Ue. d. Entwichl. u. Aushreitung der Tangtntialfasem in der menschlichen Gross- 
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Bastlan, H. C, Ue, d. specif Gewicht verschiedener Theile d, menschl. Gchims, Arch. f. 
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Bischoif, Th. L. W. v., Das ffimgewicht des Menschen, 1880. 

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Braone, WUh., Dcu GewicktsverhcUtniss der rechten zur linken Himhdlfte heim Menschen, Archiv 
fiir Anat, 1891. 

Buchstab, Beitr. z. Frage v, d. Gemchts- u, GrdssenverhSUnissen des Gthims, Abstr. in NenroL 
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Oaloxl, Del cerveUo nei due tipi bradiieephalo e dolichocephalo italiani, Bologna, 1875. 

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Conti, A., DeVipaisseurdeV6coTce du cerveau humain, Internationale Monatsschrift ftir Anatomic 
u. Physiologic, vol. i., 1884. 

Orioliton-Browne, J., On the weight of the brain and its component parts in the insane. Brain, 
Tols. 1 and 2, 1879. 

Danilewsky, B., Die quantiiativen Bestimmungen dergrauen und weitsen Suhstanzen tm Gehim, 
Central biatt f. d. medicinischen Wissensch., 1880. 

Davis, B., Contributions towards determining the weight of the brain in different races of man, 
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Donaldflon, H. H., Anatomical obserTxUions on the brain and sense organs of the blind deaf- 
mute Laura Bridgman, Journal of Psychology, vols. 3 and 4, 1890 and 1891. 

HiiBohke, E., Schddel, Him und Seelc des Menschen und der Thiere nach Alter ^ Geseklecht und 
Race, 1864. 

Jensen, J., Untersuchungen iiber die Beziehungen zwischen Grosshirn und Geistesstorung an sechs 
Gehimen gditeskranker Individuen, Archiv f. Psychiatric, vol. v., 1876 ; Unters. «. 453 nach 
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Krause, W., Ueber Gehimgewichte, Allgem. Wiener med. Zeit., 1888, and Intemat. Monatschr. f. 
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Major, H. C, ^ new method of determining the depth of gray matter of the cerebral convolutions. 
West Biding Lunatic Asylum Med. Reports, 1872. 

ICanouvrler, De la quantity dans VencSphale, M^m. de la soci^t^ de Tanthropologie, t. iii., 1888. 

Marshall, J., Relations between the weight of the brain and its parts and the stature and mass of 
the body in man. Journal of Anatomy and Physiology, July, 1892 ; The brain of the late George Grote, 
with comments and observations on the human brain and its parts generally. Ibid., Oct., 1892. 

Meynert, Th., Da^ Gesammfgemcht u. die Theilgewichte des Gehimes, <£rc., Yierteljahrsschr. f. 
Psych., 1867 ; Uc, d. Methode der Gehimv)dgungen, Mittheil. d. Wiener anthropol. Gesellsch., Bd. 1, 

Meroier, A., On the weight of ike brain in the insane with reference to the hemispheres, lobes, 
brain^stem and cerebellum, Joum. Mental Sc, vol. xxxvii., 1891. 

Panller, A. B., Reoherches sur la notion de surface en anatomic. Determination de la surface du 
cerveau, Ac, 1892. 

Snell, O., Die Abhangigkeit des Himgewichts von dem Kdrpergetncht und den geistigen Fahig- 
heiten, Archiv f. Psychiatrie, Bd. xxiii., 1891 ; Das Gewicht des Gehimes, dsc,, Munchener medic 
Wochenschr., 1892. 

Topinard, Lepoids de Venc^haU, Mem. de la soci6t^ de I'anthropologie, t. iii., 1888. 

Vierordt, H., Anatomischc, physiologiscfie und physikalische DcUen und TaheUen, 1888. 


Waffner, H., Mcuiubettimmungeii der OberJULohe da groaaen Oehirru, Inang. Diss. , Gottingen, 1864. 

Wagner, B., Vontudien ru einer wiatenackttfUichen Morphologic und Phynologie de» mensehlichen 
Gehims ah Seeleiiorgan, 1860, 1862. 

Waisbaoh, A., Die QewiehUvtrhHUfUaH d, OehimM Qsterreichiaeher Voiher^ Arch. 1 Anthrop., I., 


AdamkiewloB, Albert, Die Blutgef&tae det menaehliehen RUckenmarhet ; L Theil : Die Gefagte 
der RUekenmarkea-Subatanz, SittuDgBberichte der k. Akad. d. Wiis. in Wien, Bd. Ixxziv., 3 Abtli., 
1881 ; //. Theil: Die Gefdste der RUckenmarkes-ObetJlaehe, IbM., Bd. Ixxxt., 3 Abth., 1682 ; Die 
Arterien dee verldngerten MarkeSf Denkschr. d. Wiener Akademie, 1890. 

Browninff, The veins of the brain and it$ envdopee, Brooklyn, 1884 ; Article ** Veude of the 
Brain,*' Ref. Handbook of the Medical Sciences, vlii., 1889 ; The arrangement of the mpraurtbral 
veiiie in man, <u bearing on /JUT 8 theory of a developttiental rotation of the brain, Journal of 
NervooB and Mental Diseases, vol. 18, 1891. 

Buret, H., Sur la dittrilmtion det artiree nourriciirea du bulbe rachidien, Archives de Physiologie, 
1873 ; Recherchee anatomiques 8. I. circulation de Vene^haUf Ibid. 1874. 

H6don, B., Etude anatamique eur la eireulation veineuae de Veneiphale, Th^, 1888 ; abstract 
in International Monthly Joamal of Anatomy and Physiology, 1889. 

Huebner, Ziir Topographic der Emihrungagebiete d. einzdnen ffimarterien, Centralbl. f. d. 
med. Wissen., 1872 ; Die luetiache Erkrankung der Eimartericn, Leipzig, 1874. 

Xadyl, H«, Ueber die Blutgefdaae des menachlichen RUckenmarkea, 1889. 

Key n. Betaiua, Studien in der Anatomic dea Nervenay sterna, Stockholm, 1876. 

Koliako, Ue, d. Bexiehung d, art. chor. ant, n»m hinteren Schenkd der inneren Kapael, Wien, 

Labbd, C, Note aur la circulation veineuae du cerveau, Archives de Physiologie, 1879 ; Etude sur 
les granulations de Pacchioni, «fcc., Th^e, Paris, 1882. 

Kleraejewaky, J., Die Ventrikd dea Gehirna, Centralbl. f. d. med. Wissensch., 1872. 

Boas, Jamea, Diatributian of the Arteriea of the Spinal Cord, Brain, April, 1880. 

Boaabach u. Lehrwald, Udter die Lymphuege dea Gehirna, Centralbl. f. d. med. Wissensch., 

S6e, M., Sur la communication dea cavitia ventriculairea de Venciphale avec lea eapacea sous- 
araehnoidiena, Revue mensuelle, 1878 & 1879. 

SperlzLO, O-., Oircolazume venoaa del capo, Torino, 1884. 

Symixiffton, 1,, On the valvular arranytmenta in connection with the cranial venoua circukUum, 
Brit. Med. Journal, 1882. 

Trolard, Reeherchea aur V anatomic du ayathne veineux de Vinciphale et du crane, Th^, 1868, 
and in Archives g^n^rales de m^decine, 1870 ; Lea granulationa de Pacchioni, Jonm. de Tanatomie et 
de la physio]., t. 28 ; De quelquea particularity de la dure-m^re. Ibid., 1890. 

Valenti, Q., e.Abnndo, O., Sulla vaaeularizazione cerebrale, dtc., Atti d. soc. toscana di sci. 
natnr., vol. xi., 1890. 

Wlndle, B. C. A., On the arteriea forming the circle of Willia, Joum. of Anat. and Phys., xxi., 


Sherrington, C. 8., Notea on the arrangement of some motor fibrea in the lumbo sacral pUxns, 
Section IV. Relation of the limb to cell-groups in the spinal cord. Journal of Physiology, vol. xiii., 
No. 6, 1892. 


Abducent nerve. See Njcrve, rixtb. 
Aberrant bundle of medullary striee, 50 
Accessory auditory nucleus, 55, 60 

cuneate nucleus, 53 

iiocculi, 76 

nucleus, 20, 55 

olivary nuclei, 57 

vasal nucleus, 55 
Acermlns cerebri (dim. of duervm, heap), 1 14 
Acoustic tubercle, 50 

Affenspalte (German, ape-fissure), 143, 150, 151 
Age, influence of on brain-weight, 178, 180 
Ala cinerea (grey wing), 50 

lobuli centralis, 71, 73, 82 
Algieii on tracts of Bnrdach, 32 
Alveus (trough), 158, 172, 173 
Amygdala cerebelli {amygdaXaj tonsil), 74, 76, 82 
Amygdaloid nucleus, 124, 131, 135, 160, 169 
Amygdalo-uvular lobe, 76 
Angle, Rolandic, 143 

Sylvian, 142 
Angular gyrus, 151, 153 
Annectent (connecting) gyri, 143, 144, 145, 146, 

147, 148, 149, 150, 151, 152, 153, 156 
Ansa (loop) lenticularis, 103, 112, 114, 135, 164 

pednncularis, 112 
Anterior column of cord, 9, 12, 22, 65 

commissure of brain, 38, 98, 131, 135, 156, 

160, 164 
of cord, 6, 7, 10, 18 

marginal bundle, 25 

pillars or columns of fornix, 97, 113, 116, 
129, 131, 158 

pyramidal tract, 24, 31, 32, 45 

roots of spinal nerves, 19, 32, 94 
Antero-lateral ascending tract, 24, 25, 32, 34, 
65, 85, 103, 104 

descending tract, 24, 25, 32, ^^ 93, 94 

ground bundle, 26, 32 

white columns, 9, 24, 31, 32, 64, 86, 95, 104 
Apex cornu posterioris, 8 
Aqueduct, nucleus of, 65 

Sylvian, 96 

central grey matter, 96, 98 
epithelium of, 96 
Arachnoid {hpix^t spider or spider's web) mem- 
brane, I, 3, 137, 181, 187 
Arachnoidal villi (villus^ tuft of hair), 184, 190 
Arbor vitce (from resemblance to shrub so 

called) cerebelli, 71, 74, 76, 78 
Arched or arcuate fibres, external or superficial, 

44, 45i 58, 59 
internal or deep, 53, 

58, 93, 95' 104 
Arcuate sulci of cerebellum, anterior, middle 

and posterior, 75, 77 

Area of Broca, 159, 160 

Areas of medulla oblongata, anterior, 43, 45 

lateral, 43, 45 
posterior, 41, 43 

Arteries, cortical, 193 
of dura mater, 184 
lenticular, 197 

lenticulo-optic (lenticulo- thalamic), 197 
lenticulo-striate, 197 
medullary, 193 
of spinal cord, 191 
Arterioles, central, 192 
Artery of ** cerebral hsemorrhage," 197 
Ascending auditory fibres, 63 

cerelMllar tract. See Cerebellar Tract. 
degeneration, 24, 27 
frontal gyrus, 148, 163 
parietal gyrus, 143, 148, 150, 151, 163 
root of fifth nerve, 52, 63 
tracts, 25, 26 
Association-bundle, anterior, 165 

inferior, 165 
superior, 165 
fibres, ij8, 163, 165, 169 
of cerebellum, 84 
Auditory nerve. See Nerve. 
nucleus, 104, 106 

accessory, 55, 60 
inner or dorsal, 56, 62 
outer or superior, 56, 62 
ventral, 56, 63 
connections of, 103, 104, 106 
Auerbach on degeneration in spinal cord, 34 
Australiaus, brain- weight of, 180 
Axis, cerebro-spinal, i 

Baillargbr on grey cortex, 177 

lines of, outer and inner, 167 
Band, furrowed, 76 
Basal ganglia, 163, 172 

optic gansUon, 1x6, 120 
Basis pedunculi, 100 
Basket cells, 89, 91 
Bechterew on connections of upper olive, 60 

fillet, 65 
Beevor on cingiilum, 158 
fornix, 129 
lyra, 131 
Bellonci on optic lobes of birds, 107 
Benedikt on brain of criminals, i6x 
Bergmann's fibres, 87 
Bigeminal bodies, 106 
Birds, cerebellum of, 69 

optic lobes of, 107 
Bischotf on brain- weight, 178 
Biventral lobe of cerebellum, 74, 76, 82 
Blood-vesssels of brain and cord, 191 
Bochdalek on nerves of arachnoid, 189 
Body of fornix, 129, 158 
Body- weight, relation of brain- weight to, 178 
Bordeiing gyrus, 159 
Borders of cerebral hemisphere, 137 
Boyd on brain- weight, 178 



Brachial enlargement of cord, 5 
Brachiiim conjunctivum (connecting arm), 103 
of quadrigeminal body, 105, no, in, 
Brachycephalic (/8pax<^r, short ; Kc^a\i^, head) 

persons, brains of, 176, 177 
Brain, i, 38. See also Cerkbrum, Cerebel- 
lum, Pons, and Medulla oblongata. 

blood-vessels of, 191, 193 

commissures of, i, 38 

dimensions of, 176 

divisions of, 38 

literature of, 199 

lymphatics of, 198 

measurements of, 176 

membranes of, i, 181 

ventricles of, 38, 47, 96, 97, 122, 188, 189 

weight of, 178 . 
Brain-sand, 114 
Broca, area of, 159, 160 

on brain -weight, 178 

on grande lobe limbique, 155 
Bulb. See Medulla oblongata. 

of fornix, 115 

olfactory, 145, 159, 174, 195 

of posterior horn of lateral ventricle, 124 
Bulbus rhachiticus {l^x^h backbone), 38 
Bundle, olfactory, of cornu Ammonis, 158 

jK>8terior longitudinal, 58, 65, 66, 86, 93, 
94,95*99. 102, 109, 114, 119 
Burdach, tract of, 26, 28, 32, 44 

Caoum INATE {cammen, tip) lobe, 74, 77, 82 

Ciyal on collateral tibres, 21 
on moss-fibres, 91 
on optic lobes of birds, 107 
on spongioblasts and neuroblasts, 14 
on zone of superficial granules, 92 

Calamus scriptorius (writing pen), 47 

Calcar avis (bird's spur), 124, 144 

Calcarine fissure, 124, 143, 144, 172 

posterior, 144 

Callosal fissure or sulcus, 127, 156 
gyrus, 155, 156, 158, 160 

Calloso-marginal fissure, 145, 146, 148 

Calori on grey cortex, 177 

Canal, central of cord, 9, 10, 19 

Capsule, external, 134, 135, 164 

internal, 100, loi, 104, in, 114, 119, 128, 

131. 132, 133, I3S» 136, 163, 166, 169, 

172, 197 
Caput cornu (head of horn), 8, 51, 52 
Cat, ganglion cells of anterior nerve-roots of, 3 

pyramidal tract of, 25 
Cauaa equina (horse's tail), 3 
Caudate (cauda^ tail) nucleus, 124, 131, 134, 

I35» 136, 197 
Causation of flyri and sulci, 162 

Cavum (a hollow) Meckelii, 182 

Cell-columns of cord, 14 

of anterior horn, 14 

Clarke's, 16, 34, 86 

lateral, 16 

middle, 17 

of posterior horn, 17 

posterior vesicular, 16 
Cells, degeneration of, 24 

of Deiters, 13 

outlying, 17 

solitery, 17 

Central arterioleSi 192 

canal of cord, 9, 10, 19 

gre^ matter of mid-brain, 65, 96, 98 

gyn, 143, 148, 149, 150 

ligament of cord, 2, 5 

lobe of cerebral hemisphere, 133, 135, 145, 

154, 177 
cerebellum, 71, 73, 77 

nucleus, oculomotor, 99 
sulcus, 143 

tract of tegmentum, 60 
venules, 193 
Centre, medullary, of cerebral hemisphere, 163 
Centres, kinesthetic, 163 
psychomotor, 163, 172 
for special senses, 163 
visual, connection with cord and bulb, 1 19 
inter-connection of, 1 19 
connection with oculomotor nuclei, 
Centrifugal ai-teries of cord, 192 
Centripetal arteries of cord, 192 
Cerebellar notch, anterior and posterior, 70 

tract, antero-lateral descending, 24, 
25, 32, 86, 93, 94 
ascending bulbar, 86 
direct, 24, 25, 32, 34, 44, 65, 

dorso-lateral ascending, 24, 25, 

32, 34, 44, 65, 85, 86 
veutro-laterai ascending, 24 
25, 32, 34, 65, 85, 103, 104 
Cerebellum (dim. of cerebrum^ brain), 38, 69 
arbor vitae of, 71, 73, 74, 76, 78 
blood supply of, 195 
commissures of, 84 
connection with cortex cerebri, 86 

fibres of crusta, loi 
fourth nerve, 86 
optic tract, 120 
sixth nerve, 86, 93 
third nerve, 86 
cortex of, 87 
crura of, 46, 84 

degenerations following lesions of, 32, 93 
divisions of, 69 
fibres from posterior longitudinal bundle 

to, 103 
fissures of. See Fissures. 
hemisphei'es of, 69, 70, 78 
laminee of, 71, 72, 86 
literature of, 95 
lobes of, 1i,7^,n 
of lower animals, 69 
nuclei in white matter of, 83 
peduncles of, 38, 46, 84 

inferior, 69, 83, 86, 93, 95, 

middle, 67, 70, 83, 85, 93, 94, 

superior, 67, 69, 82, 83, 84, 
93, 94, 100, 103, 164, 195 
situation of, 69 
size of, 71 
sulci of, 71, 75, 78 
surfaces of, 71, 74 
weight of, 179, 180 
white matter of, 71, 78, 87, 91 
worm (vermiform process) of, 69, 71, 73, 74, 

77, 78, 94 
Cerebral hemispheres. See Hemibphsres. 
Cerebro-spinal fluid, i. 3, 188 



Cerebrum (brain), 38 

comparison between male and female, 179 

cortex of. See Cortex. 

crura of, 38, 96, 100, 118, 195 

fissures of. See Fissurrs. 

peduncles of, 96, 100, 135 

rotation of, 165 

weight of, 179 
See al8o Hemisphbrbs. 
Cervix comu (neck of horu), 8, 52 
Cerrical enlargement of cord, 3, 5 

nerves, effect of section of posterior roots, 28 

nucleus, 16 

region of cord, 10 
Cetaceans, brain of, 162 
Chiasma (X(^C<»> mark with letter X), olfactory, 

optic, 96, 117, 198 
Chinese, brain- weight of, 180 
Choroid (correctly chorioid, from x^P^ov, mem- 
brane) plexuses of fourth ventricle, 50, 
185, 186, 195 

of lateral ventricles, 122, 124, 155, 185, 198 

of third ventricle, 98, 185, 198 

vein, 185 
Choroidal fissure, 126, 155 

villi, 186 
Ciliary muscle, origin of nerve-fibres to, 99 
(Unguium (girdle), 129, 1^8, 165 
Cistema (reservoir) cerebeflo-medullaris, 188 

chiasmatis, 188 

corporis callosi, 188 

fossie Svlvii, 188 

interpeduncularis, 188 

lamine cinerese, 188 

peripeduncularis, 188 

pontis lateralis, 188 

media s. hasilaris, 188 
Cisteruffi arachnoidales, 188 
Clarke's column, 16, 53, 86 

effects of destruction of cells 

in, 34 
Claustrum (rampart), 134, 135. 169 
Clava (club), 143 
Clendinning on brain- weight, 178 
Clivus (slope), 70, 73, 79 
lobe of, 74, 77 
monticuli, 71 
Cochlear root of auditory nerve, 63 
Collateral eminence, 127, 145 
fibres of, 21, 65, SS, 163, 164 
fissure, 127, 144, IS3 
Columns fomicis, 129 
Columns, white, of cord, 8, 14, 22 

anterior, 9, 12, 22, 65 
antero-lateral, 9, 24, 31, 32, 

64, 86, 95, 104 
lateral, 9. 12, 64 
of Lissauer, 20, 26, 29 
posterior, 9, 26, 27, 29, 32, 53, 

postero-lateral, 7, 28, 44 

postero- mesial, 7, 10, 28, 43 

fornix, anterior, 97, 113, 116, 129 

posterior, 124, 129, 130 

medulla oblongata, 40, 41, 104 

Comet cells, 17 

Comma tract, 26, 29, 32 

Commissnra (uniting band) boseos alba, 128 

Commissural fibres of cerebKBllum. 84 

of cerebrum, 163, 164, 169, 1 72 

between hippocampi, 131 

Commissures, i 

anterior, 98, 135 
of cerebellum, 84 

of cerebrum, anterior, 38, 98, 131, 135, 156, 
160, 164 
middle, 38, 96, 97, in, 113 
posterior, 38, 98, 104, 109, 
114, 117, 119 
of cord, I, 6, 7, 10, 18, 34 
^reat, 127 

inferior, of Guddeu, 117, 118 
of Meynert, 120 

middle or soft, 38, 96, 97, in, 113 
optic, 117 

posterior, 98, 104, 109, 114, 119 
Conariam (icwvos, pine-cone), 114 
Conducting tracts of cord, 22 
Cone, fibrous, 163 
Conus medullaris, 5 
Convoluted brains, 162 
Convolutions. See Gtri. 
Cord. See Spinal oord. 
Comu Ammonis (from its resemblance to the 
horns ou the statue of Zeus-Ammon), 124, 
158, 169, 172 
Cornua of grey matter of cord, 8, 10, 32, 51, 52, 

53, 58, 104 
cell-columns of, 14 
Cornucopia (horn of plenty), 50 
Corona radiata, 107, 109, 119, 135, 136, 163 
Corpora albicantia (white boilies), s. mamillaria 
{mamillaj nipple), 96, 98, in, 113, 115, 

129, 166, 198^ 
amylacea (fiti^Kov, starch), 14 
bigemina (two), 38, 106 

geniculata (ptenu, knee), 105, 109, in, 117, 

118. 119, 195 
quadrigemina (four), 38, 96, 104, 109, no, 
117,119, 164, 195 
Corpus callosnm {callomSy hard), 38, 122, 127, 

130, 137, 156, 164, 166, 197 
absence of, 162 

peduncles of, 128, 15^, 158, 159 
Corpus trapezoides, 73, 78, 79, 82 
Cortex (bark) cerebelli, 87 
cerebri, 163 

cells of, 167 

connection with cerebellum, 86 

crusta, 10 1, 136 
hippocampal and 
callosal gyri, 158 
internal capsule, 1 36 
lower olives, 86 
upner fillet, 104 
degenerations after lesions of, 3 1 , 86, 

occipital region of, no, 136 
prefrontal region of, 136, 163 
Rolandic region of, 136 
visual area of, 1 10 
Cortical arteries, 193 
Courae of fibres in cord, 22 

of cord through medulla oblon- 
gata and pons, 63 
Cranial nerves, 93, 95 

Crescentic lobes of cerebellum, 71, 73, 74, 82 
Criminals, frontal lobe of, 161 
Crossed pyramidal tract, 24, 31, 32, 51, 64 

root of fifth nerve, 62 
Crura [eraSj leg) ad cerebrum, 84 

medullam, 86 
pontem, 85 



Crura — corUimied, 

cerebri, 38, 96, 100, 118, 195 
fornicis, 129, 130 
Cniral enlargement of cord, 5 
Crusta (rind) connection with cortex, loi, 136 
mesial bundle of, 67 

pedunculi, icx>, iii, Ii4» 115, 132, 136, 
163, 164 
Calmen (summit) monticuli, 70, 71, 73, 79 
Cnneate funiculus, 44 

lateral, 44 
lobule, 152, 197 
tubercle, 44 
Cuneo-limbic annectent gyrus, 144 
Cuneo-lingual annectent gyrus, 144 
Ouneo-quadrate annectent gyrus, 144 
Cuneiis (wedge), 143, 152, 153, 156 
Cunningham on cerebral convolutions, 162 

inferior frontal sulcus, 148 
intraparietal sulcus, 150 
Rolandic angle, 143 

Danilewsky on grey cortex, 177 
Darkschewitsch on Gudden^s commissure, 118 

optic tract, 117 
posterior commissure, 109 
Decussating commissural fibres of cerebellum, 84 
Decussation of fillet, 53 

pyramios, 46 
Degeneration of nerve- cells, 24 

nerve-tracts in spinal cord, 
ascending, 24, 27 
descending, 24, 27 
secondary, 24 
tertiary, 24 
in spinal cord from lesions in cerebellum, 

in cerebrum, 31 

long, 32 
short, 32 
Deiters, cells of, 13 

on formatio reticularis, 58 
nucleus of, 56, 62 
Dentate fissure, 156, 158 

gj'rus, 127, 155, 156, 158, 172 
De Regibus on gi*ey cortex, 177 
Descending cerebellar tract, antoro-lateraJ, 24, 
25, 32, 86, 93, 94 
degeneration, 24, 27 
horn oflateral ventricle, 122} 124, 130 
root of fifth nerve, 65, 100 
tracts, 24, 26, 94 
Dimensions of brain, 176 
Directcerebellartract, 24, 25, 32, 34, 44, 65, 85, 86 

lateral, 25 
pyramidal tract, 24, 31, 32, 45 
sensory tract, 163 
Dolichocephiuic {6o\ix6s, long ; kc^kkX^, head), 

persons, brains of, 176, 177 
Donaldson on grey cortex, 177 
1 Dorsal cell-group of anterior horn, 14 

column of medulla oblongata, 40 ' 
longitudinal bundle, 58, 65, 66, 86, 93, 

94, 99, 102, 109, 1 14, 1 19 
nucleus, 16 
oculomotor nuclei, 99 
olfactory root, 160 
part of mid-brain, 104 
region of cord, 10 
Dorso-lateral ascending cerebellar tract, 24, 25, 

32, 34, 44, 65, 85, 86 
cell-group of anterior horn, 14 

Dura mater {dura, hard ; mater, in the sense of 
that which produces or nourishes : trans- 
lated from tne Arabic), i, 3, 181 
anterior ligament of, 182 
Duret 6n artenes of brain. 197, 198 

cisterns arachnoidales, 188 
Duval on connection between third and sixth 
nerves, 63, 99 

Edinoek on fillet, 65, 103, 104 

and Westphal, nucleus of, 99 
Eighth nerve. See Nerve, Auditory. 
Elasmobranch fishes, pineal body of, 45, 115 
Eleventh nerve. See Nerve, Spinal Acces- 
Eminentia cinerea (^y eminence], 50 
collateralis, 127, 145 
teres (rounded, cylindrical), 51 
Encephalon {ip, in ; kc^oA^, head). See Brain. 
Enlar^rements of cord, 3, 5 
Ependyma {iMfut, clothing), 62, 98, 1 10, 132 
Ependymal fibres, 96 

Epidural {hrt, upon ; dura mater) space, 182 
Epiphysis (^z^vm, grow upon) cerebri, 1 14 
Ergot (French, spur), 124 
Exposed surface of cortex, 137, 177 
Extent of grey cortex, 176 
External capsule, 134, 135, 164 

geniculate body, 105, 109, iii 117, 

"9. 195 
perpendicular fissure, 144 

Extraciliar fibres, 85 

Extraventricular portion of corpus striatum, 132 

Eyes, effects of extirpation, no, 118, 119 

Facial nerve. See Nerve. 

nucleus. See Nucletts. 
Falciform lobe, 155 
Falx {/cUx, sickle) cerebelli, 182, 183 

cerebri, 137, 182 

minor, 183 

Fascia dentata (toothed bundle) Tarini, 156, 172, 

Fasciculus (small bundle) nrcuatus, 105 

longitudinal, inferior, 165 
superior, 165 

perpendicular, 165 

retroflexus, 113 

(or funiculus) teres, 50, 53, 63 

uncinate, 165 
Fasciola (small bandage) cinerea, 157, 158 
Fibres, collateral, 21, 65, 88, 163, 164 

ependymal, 96 
FibrsB propris, 165 

rectae, 59 
Fibrous cone, 163 
Fifth nerve. See Nerve. 

nuclei of. See Nucleus. 
Fillet, 53, 65, 66, 93, 109, 164 

decussation of, 53 

lateral or lower, 66, 103, 105 

mesial, 67, 101, 103 

tract of, 103 

upper, 104, 107, 114, 119, 120 

upper nucleus of, 104 
Filum (thread) terminate, 2, 5, 189 
Fimbria (fringe), 124, 130, 157, 158, 159, 166, 

Fimbrio-dentate sulcus, 157 
First nerve. See Nerve, Olfactory. 
Fishes, pituitary body of, 116 

segmentation of spinal cord in, 16 



Fissura choroideai 155 

prima, 159 

serotina (late), 159 
FissuRRs {see Sulci) of cerebellum, 71, 75,78, 79 

antero-superior, 71, 73 
great horizontal, 71, 75, 79, 82 
intraciilminate, 82 
intralobular, 72 
midventral, 77 
postclival, 71, 73. 79. 82 
postero-snperior, 71, 73 
postnodular, 75, 79 
postpyramidal. 75, 79 
preclival, 71, 73, 79, 82 
prepyramidal, 75, 79 
of cerebrum, 137 

calcarine, 124, 143, 144, 172 

posterior, 144 
callosal, 127, 156 
calloso-marginal, 145, 146, 148 
choroidal, 126, 155 
collateral, 127, 144, 153 
dentate, 156, 158 
external perpendicular, 144 

great longitudinnl, 129, 137 
ippocampal, 124, 156, 158 
interior, 124 
limbic, 155, 160 
paracentral, 145 
parallel, 153 

parieto-occipital, 124, 143, 144 
paroccipital, 150 
prelimbic, 145 

of Rolando, 143, 150, 154, 155 
of Sylvius, 141, 143, 146, 147, 

148, 150 
transverse, 124 
variations in, 161 
See also Sulci. 
of medulla oblongata, 40 
or furrows of spinal cord, 6, 7 
Flechsig on fillet, 65 

l<locculus (dim. otfloccua, flock of wool), 74, 75, 
accessory, 76 
Fluid, cerebro-spinal, I, 3, 188 

subarachnoid, 187 
Flnmina (rivers), 188 
Folia (folium, leaf) of cerebellum, causation of, 

Folium cncuminis (of the tip), 71, 74, 79 
Foramen csecum, 40 

of Majendie, 48, 188 
of Monro, 97, 122, 129 
Forceps (pincers) major, 124, 129, 166 

minor, 128 
Forel on Meynert's bundle, 114 
tegmentum, 114 
tract of fillet, 103 
pillars of fornix, 129 
Formatio reticularis, 51, 52, 58, 60, 65, 100, loi, 

102, 103, 114, 164 
alba (white), 58, 65 
grisea (grey), 58 
Formation of corn n Ammonis, 169 
Fornix (arch or vault), 122, 128, 129, 155, 158, 
159, 166 
bulbs of, 115 
pillars or columns of, anterior, 97, 113, 116, 

"9, 13^ 158 
posterior, 124, 129, 

130, 157, 158 


Fossa rhomboidalis, 47 
Sylvian, 142 
Tarini, 115 
Fourth nerve. See Nerve. 

nucleus of. See Nucleus. 
ventricle, 47, 73 

floor of, 50 
Fovea (pit) inferior, 50 
superior, 50 
Foville on taenia semicircularis, 131 
Fraenulum {frenum, bridle) veli, 104 
Frsenum lingulse, 73 
Freud on solitary cells of lamprey, 17 
Frontal convolution. See Gyrus. 

lobe, 112, 14S, 156, 160, 161, 164, 165, 177, 

180, 195 
operculum, 142 
pole of hemisphere, 137, 147 
sulci. See Sulci. 
Fronto-limbic annectont gyrus, 149 
Fronto-marginal sulcus, 146 

lateral, 146, 149 
Fron to-parietal operculum, 142 
Fuchs, brain of, 176 

Funiculus cuueatus (wedge-shaped corl), 44 

lateralis, 44 
gracilis (slender), 43 
of Rolando, 44, 52 
solitarius, 55 
(or fasciculiLs) teres, 50, 53, 63 

nucleus of, 54, 65 
Furrowed band, 76 
Fusiform lobule, 153, 166 

Galen, veins of, 185 
Gambetta, brain of, 161 

Ganglia or ganglion {ydr/yKtoy, swelling), basal, 
163, 172 

basal optic, 116, 120 

ofhabenula, 103, 113, 117 

of hemispheres, 131 

interpeduncularo, 103, 114 

optic, 109 

radicis cochlearis, 55 

of roof, 108 

of spinal nerve-roots, 3 
Ganser on quadrigeminal bodies, 107 
Gauss, brain of, 176 
Gehuchten on collateral fibres, 21 
olfactory bulb, 176 
Geniculate body, external, 105, 109, in, 117 

"9. 195 
internal, 105, 109, 118, 195 

Genu (knee) of corpus cidlosum, 128 
of fissure of Rolando, 143 
of internal capsule, 136^ 
Giacomini on brains of criminals, 161 
gyrus Rolandicus, 143 
dentatus, 157 
longus insuTfe, 155 
Gland, pineal, 96, 97, 104, 114 
Glandufee Pacchionii, 190 
Globus pallidus (pale sphere), 134, 164 
Glomeruli (dim. of glomus, clue of thread), 

olfactory, 175, 176 
Glosso-pharyngeal nerve, origin of^ 4C^ 54« 55 

nucleus, 55 
Golgi on classification of nerve-cells, 17 
collateral fibres, 22 
fascia dentata, 173 
olfactory bulb, 176 




Goll, tract of, 26, 28, 32, 34, 43 

Graaf, de, on pineal body, 115 

Gracile nuclens, 53, 86 

Grande lobe limbique, 155 

Granule-layer of cerebellar cortex, 87, 89, 90 

of olfactory bulb, 174 
Great commissure of cerebrum, 127 

horizontal fissure of cerebellum, 7 1, 75, 79f 82 
longitudinal fissure, 129, 137 
Grey commissure of cord, 7 
matter, central, 65, 98 

of aqueduct, 96, 98 
of cord, 7, 13 

connection with visual centres, 119 
effect of destruction, 34 
ganglionic or cell-columns of, 14 
horns or comua of, 8 
intermediate grey substance of, 8 
intermedio-lateral tract of, 8 
microscopic structure of, 13 
processus reticularis of, 8 
proportion of, to white matter, 7, 10 
of hemispheres, structure of, 166 
of medulla oblongata, connection with 
visual centres, 119 
olfactory root, 159, i6o 
Grooves or sulci of medulla oblongata, 40, 41 
Ground-bundle, antero-lateral, 26, 32 
Gudden, commissure of, 117, 118 

on connection between cerebellum and olive, 

optic fibres, 118 
pillars of fornix, 129 
Guinea-pig, optic chiasma of, 118 

pyramidal tract of, 25 
Gyrus or Gyri {yvposj ring), 137 

angular, 151, 153 

annectent, 143, 144, 145, 146, 147, 148, 150, 
151, 152, 153, 156 

bordering, 159 

breves insulse, 155 

brevis accessorius insulse, 155 

callosal, 155, 156, 158, 160 

causation of, 162 

central, 143, 148, 149, 150 

of central lobe, 154 

cinguli, 156 

cuneo-limbic annectent, 144 

cuneo-lingual annectent, 144 

cuneo-quadrate annectent, 144 

dentatus, 127, 155, 156, 158, 172 

fomicatus, 156, 158, 165 
effect of removal, 32 

fomicis, 155, 158 

frontal, 143, 146, 147, 148, 150, 154, 161, 

163, 165, 172, 195 
fronto-limbic annectent, 149 
geniculi, 155, 158 
hippocampal, 153, 155, 156, 158, 159, 160, 

161, 164, 165, 167 
infracalcarine, 153 
infracallosus, 155, 158, 159. 
limbicus, 158 
lingual, 156 
longus insulse, 155 
marginal, 145, 146, 148, 150, 159 
occipital, 152 

occipito-temporal annectent, 152 
orbital, 149 

parietal, 143, 148, 149, 150, 151, 163 
parieto-occipital annectent* 151, 152 
postcentral, 150  

Gyrus or Gyri — corUinved, 
postparietal, 151, 152, 153 
prccentral, 147, 148 
rectus, 149 
Rolandicus, 143 
subcalcarine, 153 
subcallosus, 155, 158, 159 
supracallosal, 155, 158 
Bupramarginal, 151, 153 
temporal, 151, 152, 153, 155 
transverse temporal, 153 
transversus insulee, 154 
uncinate, 156, 172 
variations in, i6i 

Habenula (dim. of hdbtna, thong or rein), 1 1 1 

ganglion of, 103, 113, 117 
Hemiextirpation of cerebellum, 93 
Hemisection of spinal cord, 33, 104 
Hemispheres of cerebellum, 69, 70, 78 

connection with cerebral cortex, 86 
of cerebrum, 38, 122, 137 
blood-supply of, 195 
commissures of. See Commissurfh. 
dimensions of, 176 
fissures of. See Fissures. 
ganglia of, 131 

grey matter, structure of, 166 
intimate structure of, 163 
lobes of, 137, 145 
mantle of, 135, 142, 154 
stem of, 154 
ventricles of, 122 
weight of, 178 

white matter, structure of, 163 
Hensen on oculomotor nucleus, 99 
Heubner on arteries of brain, 198 
Hill on rotation of cerebrum, 165 
Hindus, brain-weight of, 180 
Hippocampal fissure, 124, 156, 158 

gyrus^ 153, 155, 156, 158, 159, 160, 161, 
164, 165, 167 
Hippocampus (from fancied resemblance to limb 
of fabulous animal thus named) major, 
124, 130, 131, 158, 172 
minor, 124 
His on funiculus solitarins, 55 

origin of neuroglia- and nerve-cells, 14 
Hoche on ganglion-cells in anterior nerve-roots, 3 
Horizontal fissure, great, of cerebellum, 71, 75, 
sulcus, lower or lesser, 75, 77 
Horns of grey matter of cord. See Cornu. 

lateral ventricle, 122, 124, 130 
Horse, olfactory lobe of, 159 
H-shaped sulcus, 149 
Husclike on brain- weight, 180 
Hypoglossal nerve. See Nerve. 
Hypophysis {^6, under ; 4><Jw, grow) cerebri, 97, 

Incisura marsupialis (pouch-shaped notch), 70 

semilunaris, 70 
Index, occipital, 151 
Inferior fissure of cerebrum, 124 
Infracalcarine gyms, 153 
Infundibulum (tunnel), 96, 97, 98, 1 16, 198 
Innervation of orbital muscles, 99, 1 19 
Intellectual development, iufluenoeof, on dimen- 
sions of brain, 176 

on fissures and convolutions, l6l 
Inter-brain, 96 



Intercentral connections of visual apparatus, 1 19 
Interlobular fissures of cerebrum, 137 
Intermediate grey substance of cord, 8 

process, 8 

sulcus, anterior, 24 
posterior, 7 
Intermedio-lateral tract, 8 
Internal capsule, 100, loi, 104, iii, 114, 119, 
128, 131, 132, 133, 13s, 136, 163, 166, 
169, 172, 197 

medullary lamina, 112, 114, 134 
Interolivary layer, 63 
Interpeduncular ganglion, 103, 114 
Intraciliar fibres, 85 
Intraculminate fissures, 82 
Intralobular fissures of cerebellum, 72 
Intraparietal sulcus, 149, 155 
Intraventricular portion of corpus striatum, 131 
Involuted medullary lamina, 174 
Island of Reil, 133, 141, 145, 154, 164 
Isthmi lobi centralis, 135 
Isthmus of brain, 38 

of gyrus fomicatus, 156 
Iter a tertio ad quartum ventriculum, 96 

Jbloer.sma.'8 theory of causation of cerebral 
gyri, 162 

Key on cistemse arachnoidales, 188 

septum posticum of cord, 188 
Kineesthetic {KlmifftSf motion ; inrOriais, percep- 
tion) centres, 163 
Kolliker on collateral fibres, 21 

nerves of arachnoid, 189 
Krause, W., white plexuses of, 169 

Labokde on connection between third and sixth 

nerves, 63, 99 
LacunflB laterales (lateral hollows), 184, 191 
Lamina (layer), anterior and posterior perfo- 
rated. See Perforated Space. 
Laminae arcuatse gyrorum, 165 

cinerea (grey), 96, 98, 117 

cornea, 122 

medullary, inner, 112, 114, 134 
involuted, 174 
outer. III, 114, 134 

quadrigemina, 96 

septi lucidi, 155, 159 

of cerebellum, 71, 72, 86 

transversales inferiores, 77 
Lamprey, solitary cells of, 17 
Lancisi, nerves of, 127 
Lateral area of medulla oblongata, 43, 45 

cell-column of cord, 16 

cell-group of anterior horn, 14 

column of cord, 9, 12, 64 

medulla oblongata, 40 

cuneate funiculus, 44 

fillet, 66, 103, 105 

horn of grey matter, 8, 10, 32, 52 
lateral ventricle, 122, 124 

nucleus. See Nucleus. 

pyramidal tract, 24, 31, 32, 51, 64 

recess, 47, 48, 49^ 188 

sinus, 182, 184 

sulcus, 100 

ventricle, 97, 122 
Latin races, brain- weight of, 180 
Latticed layer of thalamus, 112 

Lemniscus (ribbon), 53 

Lenhoss^k on basal optic ganglion, 116 

Lenticular arteries, 197 

nucleus, loi, 112, 114, 120, 132, 136, 164, 

Lenticulo-optic (lenticulo-thalamic) arteries, 


Lenticulo-striate arteries, 197 

Leptomeninx {\eirr6s, thin ; /a^w7|, membrane), 

Lesions of cerebellum, effects of, 32, 93 

cortex cerebri, effects of, 31, 86, 164 

optic thalamus, effects of, 85 

spinal cord, effects of, 32 
Lesser horizontal sulcus, 75, 77 
Ligament, anterior, of dura mater, 182 

central, of cord, 2, 5 
Ligamentum denticulatum (derUiculus, dim. of 

dens, tooth), 3, 188, 189 
Lignla (dim. of lingua^ tongue), 49, 50 
Limbic (limbusj surrounding border) lobe, 145, 
149, 154, 155, 159, 160, 161, 165, 166 

fissure, 155, 160 
Limen insulfe (threshold of island), 155 
Line of Baillarger, inner and outer, 167 

Vicq d'Azyr, 167 
Linea splendens (brilliant), 186 
Lingual gyrus, 156 

lobule, 153 
Lingula (dim. of lingua, tongue), 48, 71, 73, 82 
Lissauer's column or tract, 20, 26, 29 
Literature of brain, 199 

cerebellum, 95 

medulla oblongata and pons, 67 

mid-brain, 120 

spinal cord, 34 
Lizard, posterior longitudinal bundle of, 102 
Lobe or Lobes, amygdalo-uvular, 76 

biventral, 74, 76, 82 

central, of hemispheres, 133, 135, 145, 154, 

of vermiform process, 71, 73, 77 
of cerebellum, 71, 74, 77 
of clivus, 74, 77 

crescentic of cerebellum, 71, 73, 74, 82 
falciform, 155 
frontal, 112, 145, 156, 160, 161, 164, 165, 

177, 180, 195 
of cerebral hemispheres, 137, 145 
inferior semilunar, 74, 77, 82 
limbic, 145, 149, 154, 155, 159, 160, 161, 

165, 166 
occipital, 112, 119, 145, 151, 153, 163, 164, 

165, 166, 177, 180, 195 
olfactory, 145, 158, 159, 164, 174 
optic, 38 

of birds, 107 
parietal, 112, 145, 149, 153, 177, i8o, 195 
of pituitary body, 1 16 
postero-superior of cerebellum, 71, 74, 82 
posterior of cerebellum, 74 
of pyramid, 77 

quadrilateral of cerebellum, 74 
slender, 74, 77 
temporal, 112, 145, 149, 152, 156, 160, 

163, 164, 165, 177, 180, 195 
temporo-sphenoidal, 152 
of under surfaQe of cerebellum, 75 
of upper surface of cerebellum, 73 
of vermiform process, 77 
Lobule, cuneate, 152. 197 
fusiform, 153, 166 

P 2 

_ . _, 



Lobale, lingaal, 153 

olfactory, anterior, 159, 160 
posterior, 159 

oval, 149 

paracentral, 149, 150 

parietal, inferior and superior, 150, 151, 
152, 166 

postcentral, 154, 155, 156 

precentral, 154, 155 

Quadrate, 149, 151, 156 
Lobulus gracilis, anterior and posterior, 75 
Lobus oacuminis, 74, 77, 82 

centralis, ^^ 

cHvi, 73, 74, 77 

culminis, 73, 77 

gracilis (slender), 77, 82 

nippocaram, 161 

infundibuii, 116 

lingiilce, 77 

lunatus (crescent-shaped) anterior, 73 
posterior, 74 

noduli, 75, 76, 77 

pyramidis, 76, 77 

tuberis, 75, 77 

uvuIbb, 76, 77 
I^ocus cocruleus (dark-blue place), 51, 98 

perforatus posticus, 115 
i^ng association fibres, 165 

degenerations, 32 
Longitudinal bundle, posterior or dorsal, 58, 65, 
66, 86, 93, 94, 99, X02, 109, 114, 119 

fissure, great, 129, 137 

sinus, inferior, 182 

superior, 152, 182, 184, 191 
Longitudinal striae, lateral or grey, 127, 155, 

157, 158 
mesial, 127, 128, 155, 157,158 
sulcus of midbrain, 104 
Lower stalk of thalamus, 112 
Lumbar enlargement of cord, 3, 5 

region of coi*d, 10 
LuBchka on arachnoidal villi, 191 

on nerves of arachnoid, 189 
Luys, nucleus of, 114, 120 

on outer olfactory root, 160 
Lymphatics of brain and cord, 198 
pituitary body, 116 
Lymph-spaces of dura mater, 184 

ner\'e-sheaths, 189 
pia-matur, 186 
Lyra (lyre), 130 

Majendie, foramen of, 48, 188 
Malays, brain- weight of, 180 
Mantle, 135, 142, 154 
Marchi on lesions of cerebellum, 32, 93 

tract of Burdach, 32 
Marginal bundle of uerve-fibres, 8, 25 

gyrus, 145, 147, 148, 150, 159 
effects of lesion, 31 
Marrow, spinal, 2 
Marshall on brain-weight, 180 
Measurements of brain, 176 
Medulla oblongata {medulla^ marrow ; oblonguSf 
greater in length than breadth, oblong), 
areas of, 41, 43, 45 

blood-supply of, 194 

columns of, 40, 41, 104 

external characters of, 38 

fissures of, 40 

form of, 39 

grooves or sulci of, 40, 41 

Medulla oblongata — continued. 
internal structure of, 51, 53 
literature of, 67 
measurements of, 39, 179 
origin of nerve-roots from, 40 
situation of, 38 
structure of, 40, 51 
Medulla spinalis (spinal marrow), 2 
Medullary arteries, 193 

centre of cerebral hemispheres, 163 
lamina, external, in, 114, 134 
internal, 112, 114, 134 
involuted, 174 
striae, 50, 59, 94 

aberrant bundle of, 50 
velum, inferior, 48, 70, 76, 78 

superior, 47, 70, 79, 82, 85, 98, 
103, 104 
Membranes of brain and cord, i, 3, 181 
Mendel on origin of facial nerve, 61 

superior cerebellar peduncle, 85 
Meninges (/i^i'i7|, membrane), 181 
Merkel on cleft in descending comu, 126, 188 
Mesencephalon (/xcVof, middle ; 4yK4^^w, brain), 

Mesial bundle of crusta, 67, 115, 164 
cell-group of anterior horn, 14 
fillet, 67, loi, 103 

longitudinal striae, 127, 128, 155, 157, 15S 
Meynert on brain-weight, 180 
bundle of, 103, 113 
commissure of, 120 
on claustrum, 135 

cortical cell-layers, 167 
nucleus fastigii, 84 
olfactory chiasm n, 160 
posterior commissure, IC9 
stratum dorsale, 114 

intermedium, 10 1 
Microscopic structure of cord, 12 

cerebellar laminae, 86 
cerebral cortex, 166 
Midbrain, 38, 96 

dorsal part of, 104 
literature of, 120 
transition from pons to, 65 
Middle cell-column, 17 

cerebellar peduncle, 38, 46, 67, 70, 83, 85, 

93, 94, 164 
horn of lateral ventricle, 122, 124 
or soft commissure, 38, 96, 97, in, 113 
Midfrontal sulcus, 146, 147 
Midgracile sulcus, 75 
Midventral fissure, 77 
Mitral cells, 174, 176 
Mole, posterior longitudinal bundle of, 103 

quadrigeminal bodies of, 105, no 
Molecular layer of cerebellar coitex, 87 

cerebral cortex, 167 
Monakow on anterior brachium, 107 
Monkey, fornix of, 129 
parallel fissure of, 153 
pyramidal tract of, 25, 31 
Sylvian fissure of, 142 
See also Quadrumana. 
Monro, foramen of, 97, 122, 129 
Monticulus (dim. of mongf mountain) of cere* 

helium, 71 
Moss-fibres, 91 
Motor cell-column, 14 

nucleus of fifth nerve, 61 
region, effects of removal, 31 



Mott on cellB of Clarke's column, i6 

section of uerve- roots, 27 
Moose, optic chiasma of, 1 18 

pyramidal tract of, 25, 31 
Munzer on degeneration in spinal cord, 34 

on tract of Burdach, 32 
Muscles, orbital, innervation of, 99, 1 19 
Myelin-sheath, development of, in cord, 22 

Nates, 105 

>iegro, brain- weight of, iSo 

lirst frontal gyrus of, 147 
Nebve or N EAVES {y§upoif, nerve), abducent 
See Nerve, Sixth. 
of arachnoid membrane, 188 
auditory, 95, 106 > 

ascending root of, 56 
cochlear root of, 63 
connection with inferior quadrige- 

minalbody, 106 
restiform body, 86 
nuclei, see Nucleus 
origin of, 55 
cranial, 93, 95 
of dura mater, 184 
eighth. See Nerve, Auditory. 
eleventh. See Nerve, Spinal acobssory. 
facial origin of, 40^ 55, 61, 63 

degeneration in, after cerebellar le- 

sions, 93 
nfth, central tract of, 62 

degeneration in, alter cerebellar lesions, 

origin of, 40, 51, 61, 65, 98 

trophic fibres of, 51 

roots of, ascending, 52, 63, 93 

degeneration after section, 53 

crossed, 62 

descending, 65, 100 

raphe, 62 

first See Nerve, Olfactory. 

fourth, 98, 102, 103 

connection with cerebellum, 86 

sixth, 66 

floeso-pharyngeal, 40, 54, 55 
ypoglossal, 93, 95 

origin of, 41, 53, 57 
of Lancisi, 127 

ninth. iS'eel^ERVE, Glosso- pharyngeal. 
oculomotor. See Nerve, Third. 
olfactory, 159, 175, 
origin of, from medulla oblongata, 40 

spinal cord, 3, 19 
optic, 93, 118 

connection with anterior quadri- 
geminal bodies, 105 
phrenic, 16 
of pia mater, 187 

pneumo-gastric. See Nerve, Vagua. 
second. See Nerve, Optic. 
seventh. See Nerve, Facial. 
sixth, connection with cerabellum, 86, 93 

fourth, 66 
third, 63, 66, 99 
origin of, 42 
spinal accessory, 16, 20, 40 
tenth. See Nerve, Vagus. 
third, 93, 95, 98, 99, 102, 103 

connection with cerebellum, 86 

sixth, 63, 66, 99 
roots of, 100 
trigeminaL See Nerve, Fifth. 

Nerve or nerves — continued. 

trochlear. See Nerve, Fourth. 
twelfth. See Nerve, Hypoglossal. 
vagus, 40, 54, SS 
Nerve-cells of cerebellum, 87 
of cord, 10, 13, 14, 34 
of cortex cerebri, 167 
degeneration of, 24 
of medulla oblongata, 53, 56, 58 
of optic lobes, icS 
Nerve-tibres of cerebral hemispheres, 163 
of cord, course of, 22 

degeneration of, 24, 27 
size of, 12 

traced through bulb and pons, 63 
Nerve-roots, spinal, 3, 11, 20, 94 
anterior, 19, 32, 43, 93 
ganglia of, 3 
posterior, 20, 29 

collateral fibres of, 21 
degeneration following section of, 27 
relation t-o spines of vertebne, 3 
>See also Nerve. 
Neurilemma (vcGpoy, nerve ; Xc/ifia, peel or skin) 

of cord, 186 
Neuroglia {rtvpov ; y\la, glue), 12, 62, 87, 92, 

96, 98, 106, 159, 167, 174 
Nidus avis (bird's nost), 76 
Ninth nerve. See Nerve, Glosso-pharynoeal 
Nodule, 74, 75 

North American Indians, brain-weight of, 180 
Notch, cerebellar, anterior, 70 

posterior, 70 
Nucleus (kernel) or Nuclei, ambiguus, 55 
amygdalae, 124, 131, 135, 160, 169 
of aqueduct, 65 
auditory, 104, 106 
accessory, 55, 60 
inner or dorsal, 56, 62 
outer or superior, 56 
ventral, 56, 63 
caudatus (tailed), 124, 131, 134, 135, 136, 

centralis, 58 
cervical, of cord, 16 
of corpus albicans, 115 
of Deitera, 56, 62 
dentatus, 82, 83, 84, 85 
dorsal, of cord, 16 
of Edinger and Westphal, 99 
emboliformis, 83 
facial, 61 

connection with oculomotor, 103 
fastigii (roof), 83, 84 
of fifth nerve, motor, 61 

sensory, lower, 62 
upi>er, 61 
of fourth nerve, 98, 102 
of funiculus cuneatus, 53, 86 
external or accessory, 53 
of funiculus gracilis, 53, 86 

teres, 54, 65 
globosus (spherical), 83 
glosso-pharyngeal, 55 
hypoglossal, 53 
lateral, of cord, 17 

of medulla oblongata, 52 
of thalamus, 112 
lateralis, 52 
lenticular, loi, 112, 114, 120, 132, 136, 

164, 197 
of Luys, 114, 120 



Nucleus or Nuclei — continued, 

oculomotor, 98, 102, 109, 114, 117, 118 

central, 99 

connection with facial, 103 

dorsal, 99 

ventral, 99 
olivary, 56 

accessory, 57 

connections of, 56, 86 

superior, 47, 60 
of optic thalamus, 112, 113, 114, 129 
pontis, 60, 86, 93, 1 01 
pyramidal, 57 

of quadrigeminal bodies, 105 
red, 103, 114 
of roof, 84 
sacral, of cord, 16 
of sixth nerve, 63 

atrophy of, 100 
spinal accessory, 20, 55 
of superficial arched fibres, 59 
tegmental, 93, 94, 103 
of third nerve. See Nucleus, Oculo- 
upper, of fillet, 104 
vagus, 55 

accessory, 55 
of white matter of cerebellum, 83 

Obex (bolt), 50 
Occipital gyri, 152 
index, 151 

lobe, H2, 119, 145, 151* iS3i 163. 164, 
165, 166, 177, 180, 195 
effect of removal, 32 
operculum, 144 

pole of hemisphere, 137, 152, 178 
region of cortex cerebri, effect of removal, 

Binus, 183 

sulcus, anterior, 144, 152 
lateral, 151, 152 
transverse, 150, 152 
Occipito-temporal annectent gyrus, 152 

region of cortex, 136 
Ocular muscles, innervation of, 99, 119 
Oculomotor nucleus. See Nucleus. 

sulcus, 100 
Olfactory bulb, 145, 159, 174, 195 
bundle of comu .Ainmonis, 158 
cells, 176 

chiasma {x^O^i mark with letter X), 160 
glomeruli (dim. of glomus, clue of thread), 

I75» 176 
lobe, 145, 158, 159, 164, 174 
lobule, anterior, 159, 160 

posterior, 159 
nerves, 159, 175 
nerve-fibres, layer of, 175, 176 
root, inner or mesial, 128, 156, 158, 159, 160 
outer or lateral, 156, 159, 160 
middle or grey, 159, 160 
upper or dorsal, 160 
sulcus, 149 

tract, 145, 156, 158, 159, 160, 164, 174 
Olivary body, 41, 45, 85 
nucleus. See Nucleus. 
peduncle, 56 
Olive, inferior, 41, 45, 86, 93, 94, 118 

connection with cerebral cortex, 
superior, 47, 60 

Operculum (cover or lid) of Burdach, 141 
frontal, 142 
fronto-parietal, 142 
of hypophysis, 182 
occipital, 144 
orbital, 142 
temporal, 142 
Optic lobes, 38 

of birds, 107 
chiasma, 96, 117, 198 
commissure, 117 
ganglion, 109 

basal, 116, 120 
optic nerve, 93, 118, 188 
radiations, 112 
recess, 97 

thalamus, 93, 96, 97, no, 122, 136, 163, 
164, 166, 195. 197 
effect of lesion, 85 
inferior peduncle of, 164 
tract, 96, 105, 107, no, in, n2, n4, 117, 
connection with cerebellum, 120 
Orbital gyri, 149 

limbs of Sylvian fissure, 142 

muscles, innervation of, 99, 119 

sulcus, 149 

surface of cerebral hemisphere, 145, 148, 

149, 195 
Origin of nerves from medulla oblongata, 40 : 

spinal nerves, 3, 19 
Osmatic {ocfidofuu, smell) mammals, 158, 159^ 

160, 161 
Outlying cells of cord, 17 
Oval lobule, 149 

Pacchioniak glands, 190 

granulations, 184 
Pachymeninx (*oxi5», thick ; m^viyC, membrane), 

Paracentral fissure, 145 

lobule, 149, 150 
Parallel fissure, 153 
Paramesial sulcus, 146, 147, 161 
Parietal convolutions, 151 

ascending, 143, 148, 150, 

151, 163 
foramen, 115 

lobe, n2, 145, 149, 155, 177, 180, 19s 
lobules, 150, 151, 152, 166 
Parieto-occipital annectent gyrus, 151, 152 

fissure, 124, 143, 144 
Parkes on brain of negro, 161 
Paroccipital fissure, 150 

Pars ascendens inferior s. postcentralis inferior 

of intraparietal sulcus, iqo 
superior of intraparietal sulcus, 
basilaris of third frontal gvrus, 147, 148 
ironto-parietalis of operculum, 142 
horizontalis s. posterior of iutraparietal 

sulcus, 150, 152 
intermedia of facial nerve, origin of, 55 
occipitalis of intraparietal sulcus, 150 
olfactoria of olfactory bundle, 158, 164 
orbitalis of operculum, 142 

of third frontal gyrus, 147 
temporalis of olfactorv bundle, 158, 164 
triangularis of operculum, 142 

third frontal gyrus, 147 
Partitions of dura mater, 182 
Paulier on grey cortex, 177 



Peacock on brain- weight, 178 
Peduncle {peduTieuliUf foot-stalk of leaf) or 
peduncles, of cerebellum, 38, 46, 84 
inferior, 69, 83, 86, 93, 95, 118 
middle, 38, 46, 67, 70, 83, 85, 93, 94, 164 
superior, 67, 69, 82, 83, 84, 93, 94, 
100, 103, 164, 195 
of cerebrum, 96, 100, 135 
of corpus albicans, 115 
of corpus callosum, 128, 155, 158, 159 
olivary, 56 

of pineal body, 113, 114, 117 
of thalamus, inferior, 164 
Peduncular tract, 65 
PeduDculus conarii, 114 

flocculi, 76, 82 
Perforated space or lamina, anterior, 112, 131, 

135, 141, 15s, 158, 
159, 165, 197 
posterior, 96, 98, 

"5, 195 
Perineural sheaths, 188 

Peripheral venules, 193 

Perivascular sheath, 186, 187 

Perpendicular fasciculus, 165 

fissure, external, 144 

Pes (foot) accessorius, 127 

hippocampi, 124 

peduncuh, icx> 

Petrosal sinus, superior. 182 

Phrenic nerve, ongin of, 16 

Pia mater {pia, translation of Arabic word, 

meaning properly thin ; maler, see Dura 

mater), I, 3, ic», 114, 122, 137, 181, 


Pillars of fornix, anterior, 97, 113, 116, 129, 

13'. 158 
posterior, 124, 129, 130, 157, 
Pineal {pinea, pine-cone) body or gland, 96, 97, 

104, 114 
peduncles of, 113, 114, 117 
eye, 115 
recess, 97 
stria, 98, 114, 129 
Pituitary body, 96, 97, 116 
Plexuses, choroid, of fourth ventricle, 50, 98, 

185, 186, 195 
of lateral ventricles, 122, 

124, 155, 185, 198 
sand of, 114 

of third ventricle, 98, 185, 
white, of cerebral cortex, 169 
Pneumo-gastric nen'e. See Neuve, Vagus. 

nucleus. See Nucleus, Vagus. 
Pole of hemisphere, 137, 147, 152, 178 
of island, 155 
of temporal lobe, 153 
Polymorphous cells, layer of, i68 
Pons (bridge) Varolii, 38, 46, 100, loi, 118, 179 

blood-supply of, 194 
dimensious of, 40 
external characters of, 38, 


internal structure of, 60 
literature of, 67 
nuclei of, 60, 86, 93 
structure of, 47 
transition to mid-brain 
from, 65 
Ponticulus (dim. of pom) , 46 

Postcentral gyrus, 150 
lobule, 154, 155, 156 
sulcus of cerebellum, 71, 73, 79, 82 
of cerebrum, 143, 150 
Postclival fissure, 71, 73, 79, 82 
Posterior area of medulla oblongata, 41, 43 
calcarine fissure, 144 
central gyms, 150 

columns of cord, white, 9, 26, 27, 29, 32, 

vesicular, 16 
of medulla oblongata, 41, 104 
commissure of cerebrum, 38, 98, 104, X09, 
114, 117, 119 
of cord, 7, 18 
cuneo-linguai anuectent gyrus, 144 
descending tract, 29 
horn or cornu of cord, 8, 10, 52, 53, 104 

of lateral ventricle, 122, 124 
intermediiite septum of cord, 7 
limb of Sylvian fissure, 141, 142 
lobe of pituitary body, 116 
longitudinal bundle, 58, 65, 66, 86, 93, 94, 

95,99, 102, 109, 114, 119 
olfactory lobule, 159 
orbital gyrus, 149 

pillars of fornix. 124, 129, 130, 157, 153 
segment of internal capsule, 136 
septum of cord, 7, 188 
spinal artery, 192 
tubercle of optic thalamus, 1 10 
Postero-lateral column of cord, 7, 28, 44 
Postero-mesial column of cord, 7, 10, 28, 43 
Postgracile sulcus, 75 
Postnodular fissure, 75, 79 
Postparietal gyrus, 151, 152, 153 
Postpyramidal fissure, 75, 79 
Precentral gyrus, 147, 148 
lobule, 154, 155 
sulcus of cerebellum, 71, 73, 79 

of cerebrum, 143, 145, 146, 148, 

155 I 

transverse, 143, 146, 155 

Preclival fissure, 71, 73, 79, 82 

Precuneate sulci, 151 

Precuneus, 151 

Prefrontal region of cortex, 136, 163 

Pregracile sulcus, 75 

Prelimbic fissure, 145 

Prepyramidal fissure, 75, 79 

Pre-liolandic sulcus, 145 

Primates, third frontal gyrus of, 148 

Process, intermediate, 8 

vermiform, 69, 71, 73,74, 77, 7^ 
effects of removal, 94 
Processes of dura mater, 182 
Processus reticularis, 8 
Projection fibres, 163, 164, 169, 172 
Prosencephalon (tFpds, before ; eyKt^aXoPf brain), 

Psychomotor {^vxHt mind ; motio, motion) 

centres, 16^, 172 
Pulvinar (cushion), no, 117, 119 
Purkinje, corpuscles or cells of, 87, 88, 91, 93 

on nerves of pia mater, 187 
Putamen (husk), 134, 197 
Pyramid of worm, 74, 76, 79 
Pyramids, anterior, 43, 45 

decussation of, 46 

large and small, layers of, 168 

posterior, 44 
Pyramidal bundles, 67, 93 



Pyramidal nuclei, 57 

tract, 93, 100, loi, 163, 164, 172 

anterior or direct, 24, 31, 32, 45 
of isthmus, 65 

lateral or crossed, 24, 31, 32, 51, 64 
section of, 31 

Quadrate lobule, 149, 151, 156 
Quadrigeminal bodies, 38, 96, 104, 109, jio, 

117, 119, 164, 195 
Quadrilateral lobe of cerebellum, 74 
Quadnimana, anterior occipital sulcus of, 152 

calcarine fissure of, 144 

intrapaiietal sulcus of, 150 

occipital lobe of, 151 

parieto-occipital fissure of, 143 

third frontal gyrus of, 148 
See also Monkey. 

Rabbit, pyramidal tract of, 25 

Kacial variations in gyri and fissures, 161 

Randwindung (Gorman, bordering convolution), 

Raphe (^o^, seam) of bulb and pons, 59, 60 

of cor|)us callosum, 127 

of midbrain, 100 
Raphe-root of fiftli nerve, 62 
Rat, pyramidal tract of, 25 
Recess, lateral, 47, 48, 49, 188 

•optic, 97 

pineal, 97 

suprapineal, 97 
Recti muscles of eye, inner^'ation of, 99 
Red nucleus, 103, 114 
Reid, J., on brain- weight, 178 
Reid, R. W., on relation between vertebral 

spines and nerve-origins, 3 
Reil, island of, 133, 141, 145, 154, 164 
Relative weight of encephalon to body, 178 
Reptiles, pineal body or, 115 

posterior longitudinal bundle of, 103 

segmentation of spinal cord of, 16 
Restiform {reatiSf rope) body, 44, 69, 85, 86 
Reticular formation, 51, 52, 58, 60, 65, icx>, 

xoi, 102, 103, 114, 164 
Reticulated white substauce, 167 
Retina, 107, 118, 119 
Retinal fibres, 1 10 
Retzius, on cistemae arachnoidalofi^ 188 

on septum posticum, 188 
Rhinencephalon {^Isy Pwos, nose ; iyK4^aKotf, 

brain), 160, 161 
Ridge, connecting, of pyramid, 76 
Rivi (streams) and rivuU, 188 
Rolandic angle, 143 

gyrus, 143 

i*egion of cortex, 136 
Rolando, fissure of, 143, 150, 154^ 155 

funiculus of, 44, 52 

substantia gelatinosa of, 8, 10, 13, 44 

cells in, 17 

tubercle of, 44, 52, 62 
Roller on auditory nerve-roots, 56 
Roof, gauglion of, 108 
Roots, of auditory nerve, 56, 63 

of facial nerve, 63 

of filth nerve. See Nerve. 

olfactory, inner or mesial, 128, 156, 158, 

I59> 160 
middle, 160 
outer or lateral, 156, 159, 160 

Roots — ctmtintied. 

olfactoiy, upper or dorsal, 160 

of optic tract, 117 

of spinal nerves. See Nerve-roots. 

of third nerve, 100 
Rostral sulci, 149 

Rostrum (beak), of corpus callosum, 128 
Rust-coloured layer of cerebellar cortex, 87 

Sachs on medullary centre of occipital lobe, 166 
Sacral nucleus, 16 
Sacro-coccygeal region of cord, 10 
Sacro-lum bar nerves, effect of section of posterior 

roots, 27 
Sasittal sulcus of midbrain, 104 
Sala on fascia dentata, 173 
Sandwich islanders, brain-weij;ht of, 180 
Schwalbe on falciform lobe, 155 
on tania semicircularis, 131 
Sclavonic races, brain- weight of, 180 
Sclerosis (ffK\rip6s, hard), 24 
Second nerve. See Nerve, Optic. 
Secondary degeneration of nerve-fibres, 24 
Section, effects of, of fillet, 53 

of nerve-roots, dorsal and cer- 
vical 8pinal.28 
sacro • lumbar 

spinal, 27 
sensory of fifth 
ner\'e, 53 
of pyramidal tract, 31 
of spinal cord, 32 
Segment of spinal cord, 3, 16 
Semicircular fibres, 85 
Semilunar lobe, inferior, 74, 77, 82 
Sensory nuclei. See Nucleus of Fifth Nerve. 
root of fifth nerve, 53 
tract, direct, 163 
Septa of cord, 7, 9, 12 
Septum lucidum (clear partition), 122, 128, 129, 

155. 159 
posterior intermediate of cord, 7 

posticum of cord, 7, 188 
Seventh nerve. See Nerve, Facial. 

nucleus of. See Nucleus, Faoiai^ 
Sexual differences in brain-weight, 178, 179, 180 

variations in gyri and sulci, 161 
Sheath, perineural, 188 

perivascular, 186, 187 
Sherrington on degeneration after cortical lesions, 

on outiyiug cells of cord, 17 
Short association fibres, 165 

degenerations, 32 
Siliqua (capsule) olivse, 45 
Sims on brain- weight, 178 
Siuger on degenerations in spinal cord, 34 

on section of nerve-roots, 27 

on tracts of Burdach, 32 
Sinus (hollow) lateral, 182, 184 

longitudinal, inferior, 182 

superior, 152, 182, 184, 191 

occipital, 183 

petrosal, superior, 183 

straight, 182, 184 
Sinuses of dura mater, 182 
Sixth nerve. See Nerve. 

nucleus of, 63 
Size of body, influence of, on convolutions, 162 
Slender lobe, 74, 77 
Smooth brains, 162 



Soft commissure, 97 
Solitary bundle, 63 

cells, 17 
Solly on fibres of anterior column, 65 
Space, epidural, 182 

perforated, anterior, 112, 131, 135, 141, 

iss, 158, 159, 165, 197 

posterior, 96, 98, 115, 195 

subarachnoid 3, 186, 187, 198 

subdural, 3, 181, 184 
Special senses, centres for, 163 
Speech-centre, 147 
Spencer on pineal eje, 115 
Sphincter pupillse, innervation of, 99 
Spinal accessory nerve, 16, 20, 40 

nucleus, 20, 55 
Spinal arteries, 191, 192 
Spinal bulb. See Medulla oblongata. 
Spinal cord or marrow, i, 2 

blood-supply of, 191 

cell-columns of. See Cell-columns. 

central canal of, 9, 10, 19 

central ligament of, 2, 5 

columns of, white. See Columns. 

commissures of, i, 6, 7, 10, 18, 34 

conducting tracts of, 22 

connective tissue of, 9 

course of nerve-libres in, 22 

degenerations in, 27 

dimensions of, 2, 3 

distribution of nerve-cells of, 14 

enlargements of, 3, 5 

features of different regions of, 10 

fibres of, traced through bulb and pons, 63 

fissui'es or furrows of, 6, 7 

form of, 3 

grey matter of, 7, 13 

See also Grey Matter. 

internal structure of, 7 

lesions of, 32 

lymphatics of, 198 

membranes of, i, 3, 181 

microscopic structure of, 12 

neurilemma of, x86 

neuroglia of, 12 

origin of nerves from, 3, 1 1 

propoi-tions of grey and white matter in. 7, 10 

relation of to vertebrae, 2 

segments of, 3, 16 

septa of, 7, 9, 12, 188 

veins of, 193 

weight of, 180 

white matter of, 9, 12 
Spinal nerves, 3, 11, 19, 94 
Spitzka on mesial fillet, 10 1 
Splenium ((nrXijWov, pad), 128 
Stalk of thalamus, anterior, 112 

lower, 112 
Stammtheil (German, stem-part), 154 
Starr on oculomotor nucleus, 99 
Stature, infiuence of, on brain-weight, 179 
Stem of hemisphere, 154 
Stieda on optic lobes of birds, 107 
Stilling on decussating fibres of cerebellum, 84 

on optic tract, 118 

on restifoiin body, 85 
Straight sinus, 182, 184 

Stratum albo-ciuereum (white-grey layer), infe- 

rius, 107 
superius, 107 

cinereum, 107 

dorsale, 114 

Stratum — continued, 

^ranulosum, 174 

intermedium, 101 

laciniosum CJ^S^^)f ^73 

lemnisci, 107 

opticum, 107 

radiatum, 173 

zonale, ^8, 107, 11 1 
Stria (furrow, streak) alba tuberis, 1 16 

medullaris, of mid-brain, 98 

pinealis, 98, 114, 129 

terminalis, no, 122 
Striae, longitudinal, lateral or grev, 127, 155, 

IS7, 158 
mesial, 127, 128, 155, 157, 


medullares sen acusticse, 50, 59, 94 

Subarachnoid fluid, 187 

space, 3, 186, 187, 198 

Subcalcarine gyrus, 153 

SubdunU space, 3, 181, 184 

Subiculum (support) cornu Amnionis, 156 

Substantia ferruginea (colour of iron-rust), 

51, 65 
gelatinosa of Rolando, 8, 10, 13, 44, 62 

cells of, 17 
centralis, 18 
innominata, 112, 135 
interansalis (between the loops), 112, 114 
nigra (black), 114 
reticularis alba, 156 
spongiosa, 13 
Subthalamic tegmental region, 112, 113, 122, 

136, 164 
Sulcus (furrow) or Sulci {see Fissures), causa- 
tion of, 162 
of cerebellum, 71, 75, 77 

arcuate, anterior, middle and posterior, 

75. 77 
horizontal, great, 71, 75, 79, 82 

lower or lesser, 75, 77 

midgracile, 75 

postcentral, 71, 73, 79, 82 

postgracile, 75 

postnoduiar, 75, 79 

postp\Tamidal, 75, 79 

preceiitral, 71, 73, 79 

pregracile, 75 

prepyrainidal, 75, 79 

valleculae, 75, 76 

of cerebral hemispheres, 137, 145, 149, 151, 

153, I54i 156 
callosal, 127, 156 

centra], 143 

centralis insulse, 154 

diagonalis, 146, 148 

extreinus, 144 

fimbrio-dentate, 157 

frontalis inferior, 146, 148 

medius, 146, X47, i6i 

mesialis, 149 

(of Cunningham), 146, 147. 

superior, 146, 148 
fronto-marginalis, 146 

lateralis, 146, 149 
fronto-orbitalis, 149 
H-shaped, 149 
inferior transverse, 143 
intraparietal, 149, 155 
limitans iusuloe, 154 
marginalia, 149 
occipitalis anterior, 144, 150, 152 



Sulcus or Sulci — continufd. 

of cerebral hemispheres — continued, 
occipitalis lateralis, 151, 1 52 

transversos, 150 
olfactory, 149 
orbitnles sagittales, 149 
orbitalis, 149 

transversus, 149 
paramesial, 146, 147, 161 
postcentralis, 143, 150 
postcentralis insulre, 155 
postcentralis superior, 150 
postlimbic, 155 
precentralis, 143, 145, 155 
inferior, 146, 148 
insula, 155 
mesialis, 145 
superior, 146 

transversus, 143, 146, 155 
precuneati, 151 
pre-Kolandic, 145 
radiatus, i46 

rectus (straight) Quadrumanonim, 148 
retrocentralis transversus, 1 50 
rostral, 149 
supraorbital, 149 
temporal, 153 
transversus anterior, X46 
inferior, 143 
occipitalis, 150 
orbitalis, 149 

precentralis, 143, 146, 153 
retro-cen trails, 150 
triradiate, 149 
of mid-brain, lateralis, 100 

lon^tudiualis, 104 
ocuTomotorii, 100 
sagittalis, 104 
transversus, 104 
of spinal cord, intermediate, 7, 24 
Sunken surface of cortex cerebri, 137, 177 
Superficial arched fibres, 44, 45, 58, 59 
Superior commissure of cerebellum, 84 
fovea, 50 
medullary velum, 47, 70, 73, 79, 82, 85, 

98, 103, 104 
olive, 47, 60 
petrosal sinus, 183 
worm, 69 
Supracallosal gyrus, 155, 158 
Supramarginal gyrus, 151, 153 
Supraorbital sulcus, 149 
Suprapineal recess, 97 
Surfaces of cerebellum, 71, 74 

cerebral hemispheres, 137, 197 
orbital, 145, 147, 148, 149, 195 
Sylvian angle, 142 
aqueduct, 96 

fissuro, 141, 143, 146, 147, 148, 150 
fossa, 142 

Table of parts of cerebellar worm and hemi- 
spheres, 78 
Tsenia (rafWo, band) of medulla oblongata, 49 

fimbrije, 158 

fomicis, 98, no, 114, 129 

hippocampi, 130 

pontis, 115 

semicircularis, 122, 124, 129, 131 
Tienise tectae (concealed), 127 
Tapetum (carpet), 124, 129 

Tartuferi on quadrigeminal bodies, 106 
Tegmental nucleus, 93, 94, 103 
Tegmentum (covering), 98, 100, 102, 112, 114, 
115, 163, 164 
subthalamic, 112, 113, 122, 164 
T^la choroidea (choroid web) inferior, 185, 186, 
superior, 185 
Temporal division of cerebral hemisphere, 137 
gyri, 151, 152, 153, 155 
lobe, 112, 145, 149, 152, 156, 160, 163, 

164, 165, 177, 180, 195 
operculum, 142 
sulci, 153 
Temporo-occipital bundle, 165 
Temporo-sphenoidal lobe, 152 
Tent of dura mater, 182 

fourth ventricle, 78 
Tenth nerve. See Nerve, Vagus. 
Tentorium (tent) cerebelli, 182 

of hypophysis, 182 
Terminal arteries, 193 

filament of cold, 5, 189 
Tertiary degeneration of nerve-fibres, 24 
Testes, 105 

Testut on taenia semicircularis, 131 
Teutonic races, brain- weight of, 180 
Thalamencephalon {thalamus, bed ; iyxt^aXow, 

brain), 96 
Thalamus, optic. See Optic Thalamus. 
Thoca (sheath), 3, 182 
Thickness of cerebral cortex, 1 77 
Third nerve. See Nerve. 
Tliird ventricle, 96, 97 
Threshold of island, 155 
Tiedemann on brain- weight, 178 
Tomentum (flock of wool, hair, &c.) cerebri, 184 
Tonsil of cerebellum, 74, 76 
Tooth on origin of facial nerve, 61 
Trabs (beam) cerebri, 127 
Tract or tracts, antero-lateral ascending, 24, 25, 
32, 34, 65, 85, 103, 104 
of antero-lateral column, 24 
antero-lateral descending, 24, 25, 32, 65, 

8s, 86 
bulbar ascending cerebellar, 86 
of Burdach, 26, 28, 32, 44 
central, of fifth nerve, 62 
of tegmentum, 60 
comma, 26, 29, 32 
conducting, of coi-d, 22 
crossed or lateral pyramidal, 24, 31, 32, 

direct pyramidal, 24, 31, 32, 45 
sensorv, 163 

cerebellar, 24, 25, 32, 34, 44, 65. 85, 86 
dorso-lateral ascending, 24, 25, 32, 34, 44, 

65, 85, S6 
of fillet, 103 

of GoU, 26, 28, 32, 34, 43 
intermedio-lateral, 8 
of Lissauer, 20, 26, 29 
olfactory, 145, 156, 159, 160, 164, 174 
optic, 96, 105, 107, no, III, 114, 117, 164 

connection with cerebellum, 120 
peduncular, 65 
posterior descending, 29 
of posterior white columns, 26 
pyramidal, 24, 31, 32, 45, 93, loi, 163, 
164, 172 
of isthmus, 65 
Tractus transversus peduncnli, ir8 



Tranflition from pons to mid-brain, 65 

Transitional tegmental region, 1 14 

Transverse fibres of cerebral hemisphere, 163, 164 

fissure, 124 

gyri. See Gyrus. 

sulcus, inferior, 143 

of mid-brain, 104 
occipital, 150, 152 
precentral, 143, 146, 155 

temporal gyri, 153 
Trapezium, 47, 104 
Trapezoidal body, 73, 78, 79, 82 
Trigeminal nerve. See Nerve, Fifth. 
Trigonum (triangle) acustici, 50 

habenulse, iii, 113, 114 

hypoglossi, 50 

interpedunculare, 100 

olfactorium, 159, 160 

vagi, 50 

ventriculi, 127 
Triradiate sulcus, 149 
Trochlear nerve. See Nerve, Fourth. 
Trophic fibres of fifth nerve, origin of, 51 
Tuber (swelling) annulare, 39 

cinereum, 96, 98, ill, 116 

posticum, 74, 77, 79 

valvulffi 8. posticum, 74, 77, 79 
Tubercle, acoustic, 50 

cuneate, 44 

of optic thalamus, anterior, 110 

posterior, no 

of Rolando, 44, 52, 62 
Tnberculum laterale s. acusticum, 50 
Turck, column of, 24 

Turner, W. A. on ori^n of facial nerve, 61 
Tnrner, Sir W. on rhinencephalon, 161 
Twelfth nerve. See Nerve, Hypoglossal. 

Uncinate gyrus, 156, 172 

fasciculus, 165 
Uncus (hook), 156, 158 

Uvula (from resemblance to uvula of soft palate), 
74, 76, 79 

Vagal nucleus, accessory, 55 

Vagus (wandering) nerve. See Nerve. 

Viulecula (dim. of vallis, valley), 70 

sulci of, 75, 76 

Sylvii, 137, 141, 158, 159 
Valve of Vieussens, 47, 70, 195 
Variations in gyri and sulci, 161 
Vein, choroid, 185 

of corpus striatum, 122, 185 

of Galen, 185 
Veins of dura mater, 1S4 

of spinal cord, 193 
Velum (sail or curtain) interpositum, 98, 1 14, 
122, 129, 185, 198 

medullary, inferior, 48, 70, 76, 78 

Velum — conUrmed, 

medullary, superior, 47, 70, 73, 79, 82, 85, 
98, 103, 104 
Vena magna Galeni, 186 

Ventricles of brain, 38, 47, 96, 97, 122, 188, 189 
of cerebral hemispheres, 122 
fourth, 47, 73 
floor of, 50 
tent of, 78 
lateral, 97, 122 
of septum, 129 
third, 96, 97 
Ventro-lateral cell -group of anterior honi, 14 
tract, ascending, 24, 25, 32, 34, 65, 85, 103 
descending, 24 
Venules, central, 193 

peripheral, 193 
Vermiform {vermiSf worm) process. See Worm. 
Vicq-d*Azyr, bundle of, 113, 115, 129, 166 

line of, 167 
Vieussens, valve of, 47, 70, 195 
Villi {villus, tuft of hair), choroidal, 186 

arachnoidal, 184, 190 
Visual area of cortex cerebri, 1 10 

centres, connection with cord and bulb, 1 19 

oculomotor nuclei, 
interconnection of, 119 
Voelckers, on oculomotor nucleus, 99 
Volkmann, on nerves of arachnoid, 189 

Wagner on grey cortex, 176 
Weight of brain, 178 
spinal cord, 180 
Weisbach on orbital sulcus, 149 

weight of brain, 178 
Wernicke on nucleus caudatus, 132 
Westphal and Edinger, nucleus of, 99 
White columns of cord. See Columns. 
commissure of cord, 6, 10 
matter of cerebral hemispheres, structure 
of, 163 
cord, 9 

microscopic structure of, 12 
proportion of to grey, 7, 10 
plexuses, 169 
substance of cerebellum, 71, 78, 87, 91 

commissural fibres n , 84 
nuclei in, 83 
Worm, 69, 71, 73, 74, 77, 78 
effects of extirpation, 94 

Zona incerta, 1 14 

Zuckerkandl on bordering g3rri, 159 

olfactory bundle, 158 
gyrus geniculi, 158 
Bupracallosus, 158 
subcallosus, 159 










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